[libcxx-commits] [libcxx] [libc++] Adds a new feature-test macro generator class. (PR #90889)

[Louis Dionne via libcxx-commits]

https://github.com/ldionne requested changes to this pull request.

This looks nice! I have some comments but this should be good to go then.

https://github.com/llvm/llvm-project/pull/90889