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

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

FWIW, I'd like to backport this to 19.x if possible. But I'll wait for a little while to see whether this turns up any issues, before filing the backport request.

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