This is no substantial change, as we already assert that the
build->target and host->target LLVM are the same, but this brings the
terminology in the file in a more consistent order, since we use
build->target for CC/CXX and bintools already.
In fact we should be passing build->target to configure always,
host->target would come into play when updating GHC's settings file
after installing.
On aarch64-darwin we have additional wrappers for install_name_tool and
strip to deal with codesigning requirements (e. g. updating the
signature / checksum after changing a binary). These wrappers don't
exist on x86_64-darwin which is why the unwrapped versions were used
before, causing the kernel to kill (some) executables produced by GHC.
CC, CXX, LD, AR, …, LLC, OPT and CLANG will be invoked by GHC's build
system at build time in the build->target role. However, since we are
passing absolute paths, they will get saved in GHC's settings file and
later invoked at runtime, when they should be host->target. This means
that the build->target and host->target tools need to be the same for
our built GHC to work properly which is what we guard using these new
asserts.
Being able to drop these asserts would be a step towards cross-compiling
GHC (as opposed to building a GHC cross-compiler which still works).
* By taking clang from llvmPackages we make sure there is no version
mismatch between LLVM (where llc and opt come from) and clang (which
previously would be taken from stdenv on darwin for example).
* Only pass CLANG if useLLVM is true. Previously we also set this if
targetCC was clang. This would cause potentially confusing behavior if
llc and opt as well as clang are provided via PATH (and GHC is
compiled with useLLVM == false), because clang from PATH would be
ignored, but not llc and opt.
Since 4c75874560 it is possible to
introspect if ld.gold is contained in the used bintools, so we can also
check if it is available before deciding to use it as done in the other
GHC derivations in 0908812372.
Make clearer the difference between `maxima` and `maxima-ecl` top-level
attributes. Use the `lisp-compiler` as a passthru for all of sage's
expressions. Add the `pname` attribute for `ecl` for compatibility with
other lisp implementations.
These targets also have NCG support, but they are tested less (in fact
SPARC seems to be untested atm) and may have issues. In such cases being
able to fallback to -fllvm without rebuilding the compiler could be
useful. OTOH GHC will default to -fasm and the backends probably work
well enough in most cases.
GHC can actually accept absolute paths for its runtime tools (except for
touch) at configure time which are then saved in
`$out/lib/ghc-${version}/settings`. This allows us to drop the wrapper
entirely if we assume that a POSIX compliant touch is in PATH when we
run GHC later.
The touch problem can presumably be fixed by either patching the
configure file of GHC (although we need to take care not to change the
touch GHC uses during its compilation) or messing with the settings file
after installation.
The rationale for dropping the wrapper PATH entry completely is that
it's always possible to invoke GHC via its library which will bypass the
wrapper completely, leading to subtly different behavior.
Binary GHCs are not touched in this commit, but ideally they'll get a
similar treatment as well, so they are more robust, although we
generally don't need to use them as a library.
Note that GHC 8.8.4 doesn't care about install_name_tool or otool, so
the respective environment variables are not set.
