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

[Alex Rønne Petersen via cfe-commits]

alexrp wrote:

Thanks for the heads up; I'll open a PR to fix that. Does passing `-integrated-as` seem reasonable for this test? Or should we just outright disable the test on AIX (and perhaps other affected platforms)?

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