[libcxx-commits] [libcxx] [libc++][test] Adds backdeployment shorthands. (PR #78204)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne approved this pull request.

I think this is a great patch. It really simplifies writing these annotations for upstream folks, and it makes it easier for vendors to maintain them.

As a follow-up, we can probably clean up some ad-hoc `stdlib=apple-libc++ && target=...` checks in the test suite and replace them with LLVM release short-hands.

https://github.com/llvm/llvm-project/pull/78204