[hwasan] Limit try-catch tests to aarch64.
HWASan C++ tests do not do well on x86_64.
Fixes
// RUN: %clangxx_hwasan %s -o %t && %run %t 2>&1 | FileCheck %s --check-prefix=GOOD
// RUN: %clangxx_hwasan %s -mllvm -hwasan-instrument-landing-pads=0 -o %t && not %run %t 2>&1 | FileCheck %s --check-prefix=BAD
+// C++ tests on x86_64 require instrumented libc++/libstdc++.
+// REQUIRES: aarch64-target-arch
+
#include <stdexcept>
#include <cstdio>
