New cargo layout

[ranger-ross]

This PR adds support for Cargo's new build-dir layout tracked in rust-lang/cargo#15010.
I opted to not modify the tests as some of them have paths and it felt like it was going to be painful to keep both layouts in tests.
I think we can update the tests when the new build-dir lands on stable. wdyt?

Also I'd appreciate if you could cut a new release once this is merged as it blocks rust-lang/rust#155439

TODO (check if already done)

• Add tests
• Add CHANGELOG.md entry
• Bumped minor version and committed lockfiles in case a release is desired
• check if you used AI on this PR

[oli-obk]

I think we can update the tests when the new build-dir lands on stable. wdyt?

yea that wfm

is there a better way to detect whether the new layout is active? Some env var or -Z flag that we could process and switch?

[ranger-ross]

is there a better way to detect whether the new layout is active? Some env var or -Z flag that we could process and switch?

There is -Zbuild-dir-new-layout (and CARGO_UNSTABLE_BUILD_DIR_NEW_LAYOUT).
Though the goal is to stabilize this soon. (The stabilization PR has already been FCP'd and we just need to enable it in rl/r so that we can update the Cargo submodule)

[ranger-ross]

btw, thank you for the quick review and release! ❤️