Cargo sets `CARGO_FEATURE_*` for all features when running a build
script:
https://doc.rust-lang.org/cargo/reference/environment-variables.html#environment-variables-cargo-sets-for-build-scripts
Some crates have build scripts (e.g. openblas-src) that rely on the
feature variables being properly set.
Since we now need several representations of features, this change
also updates `createFeatures` to be a list of features, rather than
`rustc` feature arguments. `configureCrate` and `buildCrate` then
build the required representations as-needed.
Fixes#68978
When building an environment if two paths conflict but one or both are
symbolic links and they resolve to the same real path, the conflict is
discarded because the contents of both paths are the same. One of them
is chosen and there is no need to recur into them in order to build
deeper symbolic links.
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.
