[libcxx-commits] [libcxx] [libc++][test] Raise a useful error when no -std=c++NN flag is found to work (PR #99423)

[Louis Dionne via libcxx-commits]

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

Thanks, this is a clear improvement. I've hit this in the past too and it was frustrating.

https://github.com/llvm/llvm-project/pull/99423