[clang] [clang][Driver] Support passing arbitrary args to -cc1as with -Xclangas. (PR #100714)

[Fangrui Song via cfe-commits]

MaskRay wrote:

I closed #52878 as working as intended. I think zig should specify a different `-mcpu=` or `-march=`. Sorry but I've  closed the feature request #97517 as I don't think Clang can sign up addressing a potential surge of compatibility issues "please remove the incompatible target-feature when I specify -target-feature +X"

https://github.com/llvm/llvm-project/pull/100714