[libcxx-commits] [libcxx] [libc++] Add test to ensure that the mangling of types stays the same (PR #143556)

[Louis Dionne via libcxx-commits]

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

LGTM w/ comments applies and CI green.

Windows should fail (please ensure it does, and then add `UNSUPPORTED`).

https://github.com/llvm/llvm-project/pull/143556