[llvm] [clang] [AIX] support builtin_cpu_is() for aix (PR #80069)

[Amy Kwan via cfe-commits]

================
@@ -126,4 +126,57 @@ PPC_LNX_CPU("power10",47)
 #undef PPC_LNX_DEFINE_OFFSETS
 #undef PPC_LNX_FEATURE
 #undef PPC_LNX_CPU
+
+// Definition of following value are found in the AIX header file <systemcfg.h>
----------------
amy-kwan wrote:

```suggestion
// Definition of the following values are found in the AIX header file <systemcfg.h>
```

https://github.com/llvm/llvm-project/pull/80069