[clang] [clang][driver] Remove -v from mkdir & ln -s from a test since it fails on ppc64 (PR #72924)

[Fangrui Song via cfe-commits]

MaskRay wrote:

> since it fails on ppc64

Change ppc64 to AIX. This is OS-specific instead of arch-specific. AIX mkdir doesn't provide `-v`, but other ppc64 OSes (e.g. Linux/FreeBSD) may provide `-v` even if https://pubs.opengroup.org/onlinepubs/9699919799/ does not require it.

https://github.com/llvm/llvm-project/pull/72924