libphobos: Disable libphobos.phobos/std/concurrency.d on macOS 13+ [PR111628]

libphobos: Disable libphobos.phobos/std/concurrency.d on macOS 13+ [PR111628]

The libphobos.phobos_shared/std/concurrency.d test just hangs on macOS
13 and beyond and isn't even termintated after the testsuite timeout is
exceeded.  Thus, more and more concurrency.exe processes keep
accumulating, consuming CPU time for nothing.

To avoid this, this patch skips the test on macOS 13+.  The static test
SEGVs immediately instead, but I'm skipping it too for symmetry.

Tested on macOS 15 (where it becomes UNSUPPORTED) and 12 (where it still
PASSes).

I have no idea what happens on Darwin/arm64, so currently the skipping
is restricted to Darwin/x86_64.

2025-02-10  Rainer Orth  <ro@CeBiTec.Uni-Bielefeld.DE>

	PR d/111628
	* testsuite/libphobos.phobos/phobos.exp (libphobos_skip_tests):
	Add libphobos.phobos/std/concurrency.d on macOS 13+.
	* testsuite/libphobos.phobos_shared/phobos_shared.exp
	(libphobos_skip_tests): Likewise for
	libphobos.phobos_shared/std/concurrency.d