[libcxx-commits] [libcxx] [libc++] Allow the use of extensions in the implementation (PR #79532)

[Sam McCall via libcxx-commits]

sam-mccall wrote:

(Sorry this is coming a week after the patch landed: internally we do basic correctness testing within days when we pull in the code, but only do performance testing for releases)

https://github.com/llvm/llvm-project/pull/79532