Add AIX to the test macro-same-context XFAIL list

Summary: Since the integrated assembly parser was not implemented yet for AIX and macro is not part of the native assembly dialect on AIX, the test macro-same-context is expected to fail for AIX; hence added AIX to XFAIL list.

Reviewers: hubert.reinterpretcast, daltenty, jasonliu

Reviewed By: daltenty

Subscribers: jasonliu, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D80232