Change `asan/TestCases/Darwin/malloc_zone-protected.cpp` to call abort so that...

Change `asan/TestCases/Darwin/malloc_zone-protected.cpp` to call abort so that it **always crashes**.

Summary:
This is needed because on some platforms we can't install signal
handlers and so the application just traps (i.e. crashes) rather than being intercepted
by ASan's signal handler which in the default Darwin config doesn't
exit with a crashing exit code.

rdar://problem/57984547

Reviewers: yln, kubamracek, jfb

Subscribers: #sanitizers, llvm-commits

Tags: #sanitizers, #llvm

Differential Revision: https://reviews.llvm.org/D71573