[llvm-branch-commits] [libcxx] release/20.x: [libcxx] Provide locale conversions to tests through lit substitution (#105651) (PR #136449)

[Louis Dionne via llvm-branch-commits]

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

I am fine with this backport. I looked at the failure on macOS and they look like the ones we had after the unfortunate OS update on Github runners, so I think this patch is clean. Also this patch only touches the tests.

https://github.com/llvm/llvm-project/pull/136449