[compiler-rt][test] recommit: mark asan/TestCases/Posix/fake_stack_gc.cpp as unsupported on Darwin

It's failing on the Darwin CI: https://green.lab.llvm.org/green/ since it was introduced by https://reviews.llvm.org/D157552 and the failure hasn't been resolved yet

Previous fix attempt (beae3152) did not resolve the failure, so marking it as unsupported again.

rdar://113765281