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

[Daniel Rodríguez Troitiño via llvm-commits]

drodriguez wrote:

I imagine the reason is https://github.com/llvm/llvm-project/blob/ee8394d9469a2946ffe2e7d192c593ecf3f93098/llvm/lib/Object/ArchiveWriter.cpp#L897-L904

To get the same behaviour with the default format in both `gnu`, `bsd` and `darwin`, you can use something like `file001` instead of `file1`, which adds newline padding bytes until 8 byte boundaries.

I checked Xcode's `ar` and it doesn't actually add that padding, so not sure why it was needed ~10 years ago when those lines where added.

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