[llvm] [test] llvm-ar: Fix inadvertent unXFAIL for Apple platforms (PR #159796)

[James Henderson via llvm-commits]

https://github.com/jh7370 approved this pull request.

LGTM, but maybe an Apple developer would be better placed to confirm.

@alexander-shaposhnikov / @drodriguez / @RIscRIpt can any of you help?

https://github.com/llvm/llvm-project/pull/159796