Move `build-dir` out of the workspace to `cargo-cache-home` by default
As a follow up to #14125, we've talked about changing the default for build-dir after a sufficient time of it being stabilized so people have a chance to test their builds and tools with it to prepare.
Blockers:
- Allow build scripts to stage final artifacts #13663 as any workarounds (e.g.
sdl2-sysbuild script relies on Cargo internals Rust-SDL2/rust-sdl2#1520) won't be possible anymore
Open questions:
- How long do we need to wait before making the switch over?
- See #t-cargo > build-dir tool compatibility @ 💬 for a discussion for who all may be affected
- What should the new default be?
- fix(script): Tweak cargo script build-dir / target-dir #16086 moved the
build-dirfor cargo scripts to"{cargo-cache-home}/build/{workspace-path-hash}"as a proposal for what we should do for this. - Note that at https://www.reddit.com/r/rust/comments/1o8l3qq/cargoscript_call_for_testing/njyhipl/, someone asked for a mnemonic to be used to easily identify these
build-dirs, like us adding a variable for the name of the directory the workspace is in. Granted, this would also balloon the size of the path
- fix(script): Tweak cargo script build-dir / target-dir #16086 moved the