[clang] clang: Add -fno-diagnostics-show-note-snippets flag (PR #216250)

[Hans Wennborg via cfe-commits]

zmodem wrote:

This is interesting. Looking at the demo, I'm more drawn to the verbose output, but that's probably because I'm so used to it.

I like the `-fdiagnostics-brief` idea though, that sounds like it would be useful, and while the specific flag in this PR seems somewhat niche, it makes sense as part of such an umbrella flag.

https://github.com/llvm/llvm-project/pull/216250