Coincidentally, even with this typo, most tests work anyway, so I didn't
notice it in the first place.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This is because autoconf is passing -print-prog-name=ld to the
cross-gcc, which in turn assumes a FHS compliant filesystem hierarchy
and searches ../../../../$crossConfig/bin/ld for the correct ld.
Of course, this won't work on Nix, hence we're explicitly passing the
correct LD program name.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Also update 64bit setup.ini and check whether we have a 64 bit stdenv in
order to choose the proper Cygwin version. Otherwise we now have the
setup.ini for 32bit available as well.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
So far, the VMs have always been using the native architecture, because
it was reimporting <nixpkgs> several times. Now, we propagate a list of
packages down to all sub-imports, which not only makes clearer which
dependencies a part actually has, but also will make it easier in case
we want to refactor those parts to use callPackage.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This now isolates the vmTools integration from the bootstrap process and
thus removes our fixed Windows ISO and product key. The latter can now
be provided by an attribute "windowsImage" to runInWindowsVM.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This is the last item that was missing to get a fully working
runInWindowsVM function. Apart from checking exit codes, we also now
have preVM/postVM hooks which we can use to write arbitrary constructs
around this architecture, without the need to worry about specific
details.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This function is quite similar to runInLinuxVM, but also ensures that
the builder is run decoupled of the Nix store and using the userland
inside the VM.
We're now picking up the environment variables saved in the previous
commit.
The reason we suppress all errors from the source operation is that it
would emit a ton of errors because we're trying to set read-only
variables.
Also, detecting whether the origBuilder is using the default builder
from the stdenv is currently a bit of a workaround until we have a
specialized pseudo-cross-stdenv someday in the future[TM].
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Later, when we start the actual builder, we're going to restore those
environment variables. We're using "(set; declare -p)", here, because
the former is just printing _all_ environment variables, even those not
supported, and the latter only lists specifically declared variables,
which also encludes exports.
The "declare -p" command also emits those variables in a format similar
to the "export" command.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This is mainly to make it easier to quickly change mappings, without
making room for errors such as typos.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Cygwin initializes mounts on _every_ login via SSH and doesn't keep them
consistently like on Unix systems, that's why we need to also add fstab
entries for the bind mounts to the store and xchg shares.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
We now map all guest accounts to the root user, because in the end the
permissions of the current user boil down to the build user of the Nix
builder of the host. That way it's not possible to gain more permissions
at all and just makes the VM communication a lot easier.
However, setting "writable" to yes instead of "read only" to no doesn't
change anything here, I just found it to be clearer.
Also, we now no longer need to have a "nobody" user.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This is done by putting the non-initrd /nix/store into a subdirectory,
which we then chroot to and pass along the SSH command.
Also, we now collect the exit code after the chroot command and power
off the VM thereafter, because the store is no longer shadowed and we
have still access to the busybox inside the initrd.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This should trim down possible dependencies on the base installation and
hereby reduce the need for reinstallation of the damn VM to only changes
that affect the Windows installation and the base Cygwin + OpenSSH
setup.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This now finally introduces our xchg share and also uses it for
exchanging state while suspending a VM. However, accessing the _real_
Nix store still isn't possible because we're shadowing the directory in
the initrd.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Now we're doing this at the point where we're saving the VM state.
Unfortunately it's not quite right, because the controller VM is shut
down _before_ we're saving the state, so the share gets disconnected
despite autodisconnect being deactivated during setup.
We can get around this issue by finally introducing the xchg share,
which is the last item to be implemented before we can merge to master.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Security-wise it's not a big issue because we're still sandboxed, but I
really don't want to write something like \\\\\\\\192.168.0.2\\\\share
in order to set up network shares.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
We're going to do this during the suspendedVM phase, so we're able to
more easily change the shares without reinstalling the whole VM.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This could possibly cause flapping whenever qemu is too fast in starting
up. As we are running with the shell's -e flag, the socat check also
ensures that the VDE switch is properly started and causes the whole
build to fail, should it not start up within 20 seconds.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
These stages are in particular:
* Install of the bare Windows VM with Cygwin and shut down.
* Boot up the same VM again without the installation media and dump the
VMs memory to state.gz.
* Resume from state.gz and build whatever we want to build.
Every single stage involves a new "controller", which is more like an
abstraction on the Nix side that constructs the madness described in
276b72fb93.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This is kinda stupid to do every little time the file is automatically
regenerated upstream. But let's see how often that happens and whether
it will become a major annoyance or not, and if yes, we might be forced
to include it in our source tree.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This SSH key is specifically only for accessing the installed Cygwin
within the Windows VM, so we only need to expose the private key. Yes,
you heard right, the private key. It's not security-relevant because the
machine is completely read-only, only exposed to the filesystem and
networking is not available.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
At least the largest portion of the installer, because in the end we
don't want the installer to *actually* save the state but only prepare
the base image.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
After quite a lot of fighting against Windows and its various
limitations, this new is the base architecture for installing and
accessing the Windows VM and thus the Cygwin environment inside it:
.------------.
.---> | vde_switch |
| `-[#]----[#]-'
| | |
,' .' `---.___
,' 192.168.0.1 `.
| | 192.168.0.2
,' _____[#]____ |
,' | | ______[#]______
| | Windows VM | | .--' |
| |____________| | | |
| | /|\ | .-| |
| .---------. | | | | | |
.-|-| manager |-' | | | | |
| | `---------' | | | | |
| | | | | | |
| | .-------------. | | Samba |
| | | BOOTSTRAP | | | | | |
| | |-------------| | | | | .------|
| `-| spawn VMs |-+--> | | `---| xchg | <-------.
| |-------------| | | .---^------| |
| | install |---. | `-| nixstore | <----. |
| |-------------| | | `----------| | |
|---| suspend VM | | | | | |
| `------.------' | | Controller VM | | |
| | | |_______________| | |
| .--' | /|\ VirtIO
| | __|__________:____________ | |
| \|/ | | `. | | |
| .------------. | | : | | |
| | REAL BUILD | | | .-------^--------. | | |
| |------------| | `-> | serial console | | | |
`-| revive VM | | `----------------' | | |
|------------| |------------. | | |
| build |-->| /nix/store >>>-----------|-' |
|------------| |------------| | |
| collect |<--| xchg >>>-----------|----'
`-----.------' |------------' |
| | |
\|/ | | | __ ___ | |
| |--| | | (__ -|- |
F I N I S H E D | | | |__| ___) | |
|__________________________|
This might look a bit overwhelming, but let me try to explain:
We're starting at the base derivation ("BOOTSTRAP" above), where we
actually install the Cygwin envirenment. Over there we basically fire up
a vde_switch process and two virtual machines: One is the Windows
machine, the other is a NixOS machine, which serves as some kind of
proxy between the host and the Windows machine.
The reason we're doing this, is because we don't have a lot of options
for sharing files between a stock Windows machine and the host. In
earlier experiments, I've tried to communicate with the Windows guest by
using pipes and OpenSSH, but obviously this wasn't a big speed rush (or
to say it bluntly: It was fucking slow).
Using TCP/IP directly for accessing the guest would have been another
option, but it could lead to possible errors when the port or a range of
ports are in use at the Host system. Also, we would need to punch a hole
into the sandbox of the Nix builder (as it doesn't allow networking),
which in turn will possibly undermine deterministic builds/runs (well,
at least as deterministic as it can be, we're running Windows,
remember?).
So, let's continue: The responsibility of the NixOS (controller) VM is
to just wait until an SSH port becomes available on the Windows VM,
whereas the Windows VM itself is installed using an unattended
installation file provided via a virtual floppy image.
With the installation of the basic Windows OS, we directly install
Cygwin and start up an OpenSSH service.
At this point the bootstrapping is almost finished and as soon as the
port is available, the controller VM sets up Samba shares and makes it
available as drive letters within Windows and as bind mounts (for
example /nix/store) within Cygwin.
Finally we're making a snapshot of the memory of the Windows VM in order
to revive it within a few seconds when we want to build something.
Now, the build process itself is fairly straightforward: Revive VM and
build based on existing store derivations and collect the result _and_
the exit code from the xchg share/directory.
Conclusion: This architecture may sound a bit complicated, but we're
trying to achieve deterministic and reproducable builds and/or test
runs.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
At least for x86_64-w64-mingw32, it doesn't make sense to use the native
strip tool for stripping of symbols. To the contrary it results in
unusable archive files.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
Stdenv adapters are kinda weird and un-idiomatic (especially when they
don't actually change stdenv). It's more idiomatic to say
buildInputs = [ makeCoverageAnalysisReport ];
This is useful for non-Autoconf-based packages, since GNU Make's
default for CXX is "g++". (The CC default is "cc" so should work fine
with Clang already.)
Some packages in the llvm suite (e.g. compiler-rt) cannot be built
separate from the build of llvm, and while some others (e.g. clang) can
the combined build is much better tested (we've had to work around
annoying issues before). So this puts llvm, clang, clang-tools-extra,
compiler-rt, lld, lldb, and polly all into one big build (llvmFull).
This build includes a static llvm, as dynamic is similarly less tested
and has known failures.
This also updates libc++ and dragonegg. libc++ now builds against
libc++abi as a separate package rather than building it during the
libc++ build.
The clang purity patch is gone. Instead, we simply set --sysroot to
/var/empty for pure builds, as all impure paths are either looked up in
the gcc prefix (which we hard-code at compile time) or in the sysroot.
This also means that if NIX_ENFORCE_PURITY is 0 then clang will look in
the normal Linux paths by default, which is the proper behavior IMO.
polly required an updated isl. When stdenv-updates is merged, perhaps we
can update the isl used by gcc and avoid having two versions.
Since llvm on its own is now separate from the llvm used by clang, I've
removed myself as maintainer from llvm and will leave maintenance of
that to those who are interested in llvm separate from clang.
Signed-off-by: Shea Levy <shea@shealevy.com>
Install names need to be absolute paths, otherwise programs that link
against the dylib won't work without setting $DYLD_LIBRARY_PATH. Most
packages do this correctly, but some (like Boost and ICU) do not.
This setup hook absolutizes all install names.
nix-prefetch-git does not convert relative submodule urls into absolute
urls based on the parent's origin. This patch adds support for
repositories which are using the relative url syntax.
All JARs in $pkg/share/java (for each $pkg in the build inputs) are
added to $CLASSPATH. Thus, you can say
buildInputs = [ setJavaClassPath someJavaDependency ];
and the JARs in someJavaDependency will be found automatically by
tools like javac or ant.
Note that the manual used to say that JARs should be installed in
lib/java; this is now share/java, following the Debian policy:
http://www.debian.org/doc/packaging-manuals/java-policy/x110.html
The directory share/java makes more sense because JARs are
architecture-independent. (Also, a quick grep shows that we were not
exactly consistent about this in Nixpkgs.)
disabled by setting 'strictConfigurePhase' to 'false'
This is necessary for some packages, like dns, because cabal warns about
multiple versions of the same dependency being used, but the usage is fine,
actually, so we want the build to succeed. Packages that depend on 'doctest'
also have this issue <https://github.com/sol/doctest-haskell/issues/69>.
Before this commit, if a haskell library X depends on Y, and X was added to
systemPackages, only X would be available in the user environment. Y
would not be avialable, which causes X to be broken. This commit solves
the issue by setting propagatedUserEnvPkgs to all packages X depends
on when X is a library.
This adds nix-run, which is a thin wrapper around nix-build.
nix-run calls nix-build, and then executes the resulting build.
If no executable artifact is built, nix-runs outputs an error
message.
myEnvRun calls myEnvFun and builds a script that directly runs
the load-env-* script.
Together, nix-run and myEnvRun allows you to set up an environment
that can be loaded in this way:
envs.nix:
{
gcc = myEnvRun {
name = "gcc";
buildInputs = [ gcc ];
};
}
$ nix-run -A gcc envs.nix
You end up directly in your environment without having to do
nix-env -i. You will always have a fresh environment and you
don't have to pollute you profile with a lot of env packages.
The nix-prefect git script was broken when trying to parse certain
groups of submodules. This patch fixes the url detection for submodule
repositories to use the more reliable `git config` commands.
* There now is full support for building Haskell packages as shared libraries
for GHC versions 7.4.2 or later. The Cabal builder recognizes the following
attributes:
- enableSharedLibraries configures Cabal to build of shared libraries in
addition to static ones. This option requires that all dependencies of
the package have been compiled for use in shared libraries, too.
- enableSharedExecutables configures Cabal to prefer shared libraries when
linking executables.
The default values for these attributes are arguments to the haskellPackages
expression.
* Haskell builds now run in a LANG="en_US.UTF-8" environment to avoid plenty
of build and test suite errors. Without this setting, GHC seems unable to
deal with the UTF-8 character encoding that's generally considered standard
in the Haskell world.
* The Cabal builder supports a new attribute 'testTarget' to specify the exact
set of tests to be run during the check phase.
* The ghc-wrapper attribute ghcVersion has been removed. Instead, we use the
ghc.version attribute, which exists in unwrapped GHC derivations, too.
The default target (i386-linux) causes flags like "-march i386" to be
added, which breaks on recent Fedora releases (18 and up), resulting
in errors like:
/usr/lib/gcc/i686-redhat-linux/4.7.2/../../../../include/c++/4.7.2/ext/atomicity.h:48: undefined reference to `__atomic_fetch_add_4'
So set the target to i686-linux.
http://hydra.nixos.org/build/6567357
We cannot pass the --{enable,disable}-executable-dynamic flags to GHC
versions prior to 7.4.x.
Building shared libraries via --{enable,disable}-shared is possible in theory
with GHC 6.12.x or later, but doesn't work in practice because our GHC 6.10.x
builds don't provide shared versions of their base libraries. This could
probably be fixed, but it's probably not worth the effort.
enableSharedLibraries configures Cabal to build of shared libraries. This
option requires that all dependencies of the package have been compiled
for use in shared libraries, too.
enableSharedExecutables configures Cabal to prefer shared libraries when
linking executables.
This patch partly fixes issue #1084.
Kept the old hacks where they don't break the build in case they things
they fix are still relevant.
I checked that the upgrade doesn't break:
1) Asymptote and EProver builds.
2) My XeLaTeX demo from configurations/ repository.
3) Some of my own files.
The upgrade fixes problems with simultaneous use of 3D and LaTeX labels
in Asymptote.
Please provide a test that worked previously and is broken now if you
need to revert this update or its parts.
The dns packages requires this feature, because it ships two test programs: one
of them requires network access (so we cannot run it), but the other test does
not. Setting testTarget appropriately allows us to run only one of the two
suites.
Haskell packages that contain non-ascii characters in their .cabal file
or somewhere else in their haddock documentation fail to compile under
nixpkgs and usually flagged with noHaddock = true. I wanted to do the
same for modularArithmentic, when I realized that we just have to set
the locale to some UTF-8 compatible locale in build-support/cabal to fix
this issue correctly.
Wheezy has been released on June 15th and on all mirrors the SHA256 hash
of Packages.bz2 has changed to reflect the new release, so let's update.
Here is the release announcement from Debian:
http://www.debian.org/News/2013/20130615
It also seems that the versioning scheme has changed in version 7.x, so
they seem to have switched to a two digit versioning scheme. This means,
that the attribute name "debian70..." should really be something like
"debian7...", but I'm keeping the attribute as-is to not break
references.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
This is needed in order to prevent services from starting while
populating the image with the contents of the .deb files. The procedure
used here is exactly the same as used in debootstrap.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
9p (with caching enabled) is much faster than CIFS and doesn't require
Samba or virtual networking. For instance, building GNU Hello with
CIFS takes ~323s on my laptop, but with 9p it takes 54s.
More measurements will be needed to see if "cache=fscache" is really
faster than "cache=loose" (the former seems to be a little bit
faster).
This only ever worked because runInLinuxVM happened to call
overrideDerivation, which itself erroneously passed arbitrarily-added
attributes to the new call to derivation.
Hopefully this time Eelco won't have to revert my change ;)
Signed-off-by: Shea Levy <shea@shealevy.com>
Conflict in kerberos, which was updated both in master and in
stdenv-updates. Kept the stdenv-updates version, except pulled in the
enableParallelBuilding change from master.
Signed-off-by: Shea Levy <shea@shealevy.com>
Conflicts:
pkgs/development/libraries/kerberos/krb5.nix
The wrapper script accumulated some cruft over the last couple of months
because we did changes in freaky ways to avoid triggering re-builds of all
Haskell packages. Most of these kludges have been thrown out now.
This patch doesn't change the behavior of the wrapper except for one thing: the
internal helper scripts "ghc-get-packages.sh" and "ghc-packages.sh" are no
longer installed in the bin directory of the generated derivation.
The previous implementation used the following tying-the-knot trickery to
override 'doCheck' to false for the given build:
cabalNoTest = {
mkDerivation = x: rec {
final = self.cabal.mkDerivation (self: (x final) // { doCheck = false; });
}.final;
};
That seemed to work, but for some reason it caused trouble with some builds --
not all -- that use jailbreakCabal. The problem was the 'stdenv' attribute
couldn't be evaluated properly anymore:
$ nix-build ~/pkgs/top-level/release-haskell.nix -A optparseApplicative.ghc6104.x86_64-linux --show-trace
error: while evaluating the attribute `drvPath' at `/nix/store/qkj5cxknwspz8ak0ganm97zfr2bhksgn-nix-1.5.2pre3082_2398417/share/nix/corepkgs/derivation.nix:19:9':
while evaluating the builtin function `derivationStrict':
while instantiating the derivation named `haskell-optparse-applicative-ghc6.10.4-0.5.2.1' at `/home/simons/.nix-defexpr/pkgs/build-support/cabal/default.nix:40:13':
while evaluating the derivation attribute `configurePhase' at `/home/simons/.nix-defexpr/pkgs/build-support/cabal/default.nix:107:13':
while evaluating the function at `/home/simons/.nix-defexpr/pkgs/lib/strings.nix:55:26':
while evaluating the attribute `outPath' at `/nix/store/qkj5cxknwspz8ak0ganm97zfr2bhksgn-nix-1.5.2pre3082_2398417/share/nix/corepkgs/derivation.nix:18:9':
while evaluating the builtin function `getAttr':
while evaluating the builtin function `derivationStrict':
while instantiating the derivation named `jailbreak-cabal-1.1' at `/home/simons/.nix-defexpr/pkgs/build-support/cabal/default.nix:40:13':
while evaluating the derivation attribute `nativeBuildInputs' at `/home/simons/.nix-defexpr/pkgs/stdenv/generic/default.nix:76:17':
while evaluating the function at `/home/simons/.nix-defexpr/pkgs/lib/lists.nix:135:21':
while evaluating the attribute `buildInputs' at `/home/simons/.nix-defexpr/pkgs/build-support/cabal/default.nix:22:17':
while evaluating the builtin function `filter':
while evaluating the function at `/home/simons/.nix-defexpr/pkgs/build-support/cabal/default.nix:22:60':
while evaluating the function at `/home/simons/.nix-defexpr/pkgs/top-level/haskell-packages.nix:119:17':
while evaluating the function at `/home/simons/.nix-defexpr/pkgs/lib/customisation.nix:61:22':
while evaluating the function at `/home/simons/.nix-defexpr/pkgs/lib/customisation.nix:56:24':
while evaluating the builtin function `isAttrs':
while evaluating the function at `/home/simons/.nix-defexpr/pkgs/development/libraries/haskell/Cabal/1.14.0.nix:1:1':
while evaluating the function at `/home/simons/.nix-defexpr/pkgs/top-level/haskell-packages.nix:113:20':
while evaluating the attribute `final' at `/home/simons/.nix-defexpr/pkgs/top-level/haskell-packages.nix:114:7':
while evaluating the function at `/home/simons/.nix-defexpr/pkgs/build-support/cabal/default.nix:9:5':
while evaluating the function at `/home/simons/.nix-defexpr/pkgs/stdenv/generic/default.nix:51:24':
while evaluating the attribute `meta.license' at `/home/simons/.nix-defexpr/pkgs/development/libraries/haskell/Cabal/1.14.0.nix:17:5':
infinite recursion encountered
I tried to figure out why this happens, but eventually gave up. The new
implementation passes an argument called 'enableCheckPhase' to the Cabal
builder, which determines whether the user-specified doCheck value has any
effect or not. Now, a normal override can be used to disable unit testing.
It's quite amazing that we've managed to pass incorrectly spelled command line
flags to Cabal for ages without ever noticing. :-)
The search path options --extra-{include,lib}-dirs are usually unnecessary,
because the build environment is set up such that gcc and ld find those headers
and libraries automatically, i.e. without needing extra flags. The bubble burst
on MacOS X, though, where the build of haskell-text-icu couldn't find the icu
library without manually setting DYLD_LIBRARY_PATH in that build. Fortunately,
cabal takes care of that issue if a correctly spelled --extra-lib-dirs flag is
passed.
- The option for cloning in nix-prefetch-bzr is removed
- ssl certificates are now ignored by fetchbzr
This means that no .bzr directory is downloaded. Without this change, the
hash of the result is unpredictable, probably because of timestamping in the
.bzr directory.
Currently, the only package using fetchbzr is kicad.
There are some SVN repositories out there which don't have revision information
tied to externals. By using ignoreExternals, fetchsvn won't fetch these
externals anymore, so the fetch won't fail with a checksum mismatch, should
there be some changes in some of those external repositories.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>
An aggregate is a trivial build that depends on other builds. This is
intended to provide a declarative replacement of Hydra's "view"
mechanism.
For instance, you can define an aggregate named "critical" that
depends on a selected set of jobs:
critical = releaseTools.aggregate
{ name = "foo-${tarball.version}";
members =
[ tarball
build.x86_64-linux
...
];
meta.description = "Release-critical builds";
};
The "critical" build will only succeed if all its members
(dependencies) succeed.
Conflicts:
pkgs/development/libraries/libxslt/default.nix
Commit 1764ea2b0a introduced changes to libxslt
in an awkward way to avoid re-builds on Linux. This patch has been simplified
during this merge.
uses for its core libraries, so that these files integrate seamlessly into one
profile, living right next to each other. This change is eventually going to
simply our with-packages wrapper quite a bit.
This branch refactors xfce and updates it to 4.10. I had been hoping to
find someone besides Vlada to test this (I don't use xfce), but no one
has come forward yet in 2 weeks so if this breaks something they can
make an issue or fix it. It all looks good by inspection.
According to <http://hackage.haskell.org/trac/ghc/ticket/4013>, this
feature won't work with XCode versions older than 3.2.
This means that Mac users will have considerably larger binaries because
some build-time dependencies (such as HTTP) will be mis-detected as
run-time dependencies.
In the master branch, doCheck defaults to 'false', which means that no package
will change its hash unless its doCheck field is set to 'true' explicitly. In
the stdenv-updates branch, however, all Haskell packages have a default setting
of 'doCheck=true'. Once that branch has been merged, filtering doCheck is no
longer necessary.
Conflicts:
pkgs/applications/networking/browsers/chromium/default.nix
pkgs/top-level/all-packages.nix
Merge conflicts seemed trivial, but a look from viric and aszlig would be nice.
This patch configures all Cabal builds with '--enable-split-objs' unless the
Nix expression explicitly sets "enableSplitObjs = false". The Cabal manual [1]
describes this option as follows:
| The GHC -split-objs reduces the final size of the executables that use the
| library by allowing them to link with only the bits that they use rather
| than the entire library. The downside is that building the library takes
| longer and uses considerably more memory.
One immediate benefit of this change is that the 'darcs' closure defined in the
top-level no longer refers to GHC. The same is probably true with other
executable packages.
[1] http://www.haskell.org/cabal/users-guide/installing-packages.html#setup-configure
