[compiler-rt] [compiler-rt] Fix test ifdefs and XFAILs (PR #160687)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

This should fix failing tests that I've run into in my nightly build at https://github.com/mstorsjo/llvm-mingw/actions/runs/17993746384/job/51211649698.

https://github.com/llvm/llvm-project/pull/160687