[Dexter] Extend XFAIL of Dexter tests to all MacOS architectures. (#83936)

I am trying to bring up a MacOS buildbot targeting x86 and noticed that
two Dexter tests were failing,
cross-project-tests/debuginfo-tests/llgdb-tests/static-member.cpp and
cross-project-tests/debuginfo-tests/llgdb-tests/static-member-2.cpp.
Looking in the history for these tests, they were XFAILed for Apple
Silicon in 9c466062 and are failing similar on x86 for me, so we should extend
the XFAIL to all MacOS architectures.