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

[Hubert Tong via cfe-commits]

hubert-reinterpretcast wrote:

Passing `-integrated-as` does not help because it is used on AIX to control whether object files are generated directly or not (for C/C++ source).

> Or should we just outright disable the test on AIX (and perhaps other affected platforms)?

XFAIL would be good.

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