[NFC][AIX]Disable precompiled module file tests on AIX

The PCH reader looks for `__clangast` section in the precompiled module file, which is not present in the file on AIX, and we don't support writing this custom section in XCOFF yet.

Reviewed By: daltenty

Differential Revision: https://reviews.llvm.org/D114481

GitOrigin-RevId: 06d4a76309cd97e25859770b3da29006ccac421a
4 files changed