[libcxx-commits] [libcxx] Revert "[libc++] Allow the use of extensions in the implementation (#79532)" (PR #85792)

[Louis Dionne via libcxx-commits]

ldionne wrote:

I would support the revert until we understand the issue better and how to fix it. 50% regression is... very serious. Especially given all the efforts we do to reduce compile times by a few percentage points.

I'll let Nikolas have a look but that's my opinion.

https://github.com/llvm/llvm-project/pull/85792