[clang] [clang][Driver][test][NFC] Adjust test for targets with no cc1as (PR #140490)

[Hubert Tong via cfe-commits]

hubert-reinterpretcast wrote:

This PR addresses the failure seen in https://lab.llvm.org/buildbot/#/builders/64/builds/3661/steps/6/logs/FAIL__Clang__no-integrated-cpp_c.

https://github.com/llvm/llvm-project/pull/140490