xchg is advertised as a bidirectional exchange dir, but file content
transfer from host to VM fails due to caching:
If a file is read in the VM and then modified on the host, subsequent
re-reads in the VM can yield old, cached data.
This is caused by the use of 9p's cache=loose mode that is explicitly
meant for read-only mounts.
9p doesn't provide any suitable cache modes, so fix this by disabling
caching.
Also, remove a now unnecessary sync in the test driver.
This adds the `validatePkgConfig` hook, which can be used to validate
pkg-config files in the output(s). Currently, this will just run
`pkg-config --validate` on all `.pc` files, capturing errors such as
the issue that was fixed in #87789.
The hook could be extended in the future with more fine-grained
checks.
In https://github.com/NixOS/nixpkgs/pull/58431 the authors ensured that
the resulting layer.tar would always list
/nix/
/nix/store/
first to fully comply to the tar spec. Various refactorings later it is only
ensured to create /nix/ but NOT /nix/store anymore. Instead tar transformed
them to /nix/nix and /nix/nix/store.
This is much better because then we can freely keep the comments up to
date without causing mass rebuilds.
Someday, somebody should make the same change with `cc-wrapper` and
`bintools-wrapper`.
There are several tarballs (such as the `rust-lang/rust`-source) with a
`Cargo.toml` at root and several sub-packages (with their own Cargo.toml)
without using workspaces[1].
In such a case it's needed to move into a subdir to only build the
specified sub-package (e.g. `rustfmt` or `rsl`), however the artifacts
are at `/target` in the root-dir of the build environment. This breaks
the build since `buildRustPackage` searches for executables in `target`
(which is at the build-env's root) at the end of the `buildPhase`.
With the optional `buildAndTestSubdir`-argument, the builder moves into
the specified subdir using `pushd`/`popd` during `buildPhase` and
`checkPhase`.
Also moved the logic to find executables and libs to the end of the `buildPhase`
from a custom `postBuild`-hook to fix packages with custom `build`/`install`-procedures
such as `uutils-coreutils`.
[1] https://doc.rust-lang.org/book/ch14-03-cargo-workspaces.html
