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

[Fangrui Song via cfe-commits]

https://github.com/MaskRay approved this pull request.

LGTM!

(I will have limited internet access between April 20th and May 4th, and my response time may be delayed..)


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