[clang] [clang][Driver][test] Fix Driver/solaris-ld.c on non-Unix hosts (PR #138466)

[Fangrui Song via cfe-commits]

MaskRay wrote:

It's not due to non-Unix hosts. It's likely due to these builds setting CLANG_DEFAULT_RTLIB and CLANG_DEFAULT_UNWINDLIB.

https://github.com/llvm/llvm-project/pull/138466