[libcxx-commits] [libcxx] [libcxx][test] Change UNSUPPORTED to XFAIL for target-related failures (PR #81513)

[Louis Dionne via libcxx-commits]

ldionne wrote:

It looks like we have a few XPASSes on macOS back-deployment too!

```
apple-libc++-backdeployment.cfg.in :: std/thread/futures/futures.async/async_race.38682.pass.cpp
apple-libc++-backdeployment.cfg.in :: std/thread/thread.condition/notify_all_at_thread_exit_lwg3343.pass.cpp
apple-libc++-backdeployment.cfg.in :: std/utilities/format/format.range/format.range.fmtstr/format.pass.cpp
apple-libc++-backdeployment.cfg.in :: std/utilities/format/format.range/format.range.fmtstr/parse.pass.cpp
```

`std/thread/futures/futures.async/async_race.38682.pass.cpp` should stay `UNSUPPORTED`, since it looks like this test may or may not actually fail, it tries to reproduce a race condition.

`std/thread/thread.condition/notify_all_at_thread_exit_lwg3343.pass.cpp` is in the same kind of situation.

The other two `format` tests seem to have been marked as `UNSUPPORTED` via copy-paste, they don't need to be marked as such I think.

https://github.com/llvm/llvm-project/pull/81513