[libcxx-commits] [libcxx] Enable u16string_test for libcxx (PR #79499)

[Nikolas Klauser via libcxx-commits]

https://github.com/philnik777 commented:

This test is never actually run in the CI. I'd really like to get this working again before changing anything in the test itself.

https://github.com/llvm/llvm-project/pull/79499