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

[Louis Dionne via libcxx-commits]

ldionne wrote:

> 
> (Personally I find this solution a bit iffy: we've added a bunch of load onto a compiler subsystem, and immediately found circumstances where that causes problems - it seems more robust to remove the load than to patch around those circumstances. But that's a concern for owners - this will solve my immediate problem)

At the same time, we do want the ability to use extensions in the code base, which this revert prevents.

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