[libcxx] [libcxxabi] [libunwind] [llvm] [runtimes] Probe for -nostdlib++ and -nostdinc++ with the C compiler (PR #108357)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

Ok, so with https://github.com/llvm/llvm-project/pull/120370 landed, I guess we could consider trying to reland this.

By doing that, we would however break doing msan+libcxx builds unless using the very latest Clang (while libcxx in general supports building with the last two stable releases of Clang). Do you think this is an issue, or are we ok with implicitly requiring the very latest for this particular configuration?

https://github.com/llvm/llvm-project/pull/108357