[clang] [NFC][PowerPC][clang] Update clang/test/Driver/aix-default-target-triple.c for AIX specific targets (PR #147584)

[Hubert Tong via cfe-commits]

================
@@ -3,6 +3,7 @@
 // and doesn't fall back to "unknown" due to constructor ambiguity.
 
 // REQUIRES: system-aix
+// SUPPORTED: target={{.*}}-aix{{.*}}
----------------
hubert-reinterpretcast wrote:

```suggestion
// REQUIRES: system-aix, target={{.*}}-aix{{.*}}
```

https://github.com/llvm/llvm-project/pull/147584