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

[Mark de Wever via libcxx-commits]

mordante wrote:

I would also support a revert until we can found out what caused the regression.

@sam-mccall what modules are you talking about Clang modules or C++20 modules?

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