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

[Martin Storsjö via llvm-branch-commits]

mstorsjo wrote:

So, this backport in itself should be clean, but running libcxx CI on the 20.x release branch is broken and would require a few other backports, that are entangled. So it's basically up to @ldionne if he thinks it's ok to merge despite the unrelated CI failures. (It is tricky because those failures _are_ in the same area; updated macOS changed locale definitions, which would require similar changes like these, plus more, to get a green run there. 95d23f58b6bc8e31a5a2f027338c1f6ecab1a0f1 on git main just marks those tests as unsupported...)

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