[libcxx-commits] [libcxx] [libc++] Add testing configurations for libstdc++ and a native stdlib (PR #98539)

[Louis Dionne via libcxx-commits]

ldionne wrote:

This is a start. It's not perfect but it works and we can build on top of that, so I'll merge this.

https://github.com/llvm/llvm-project/pull/98539