[llvm-branch-commits] [libcxx] release/19.x: [libcxx] don't `#include <cwchar>` if wide chars aren't enabled (#99911) (PR #106788)

[Louis Dionne via llvm-branch-commits]

https://github.com/ldionne approved this pull request.

We saw some breakage internally that is fixed by this patch and that's why I believe this regression fix is worth cherry-picking.

https://github.com/llvm/llvm-project/pull/106788