[clang] [Driver] Add -Wa, options --crel and --allow-experimental-crel (PR #97378)

[James Henderson via cfe-commits]

https://github.com/jh7370 commented:

I've skimmed through this, and it looks okay, but I don't have enough experience with the clang driver to feel comfortable signing it off.

https://github.com/llvm/llvm-project/pull/97378