[clang] [llvm] Use %errc to get text for system errors (PR #109852)

[David Spickett via cfe-commits]

DavidSpickett wrote:

I think https://github.com/llvm/llvm-project/blob/5a191e3cd904b5fee202569e54fe04f91f1a697f/llvm/utils/lit/lit/llvm/config.py#L411 works such that if the messages cannot be found (cross compiling and such) we default to asking Python what it thinks they should be.

I wondered if these tests needed some "UNSUPPORTED: no_errc" but this means that they don't.

https://github.com/llvm/llvm-project/pull/109852