[libcxx-commits] [libcxx] [libc++] Use public os_sync API instead of private __ulock on newer Apple platforms (PR #182947)

[Louis Dionne via libcxx-commits]

ldionne wrote:

Closing in favour of #202519 since I can't seem to push to this PR to resolve merge conflicts and fix the remaining comments.

https://github.com/llvm/llvm-project/pull/182947