[AArch64][NFC] require aarch64 support for hwasan test

This was breaking builds where the target is not enabled.

Reviewed By: danielkiss, eugenis

Differential Revision: https://reviews.llvm.org/D85412

Author: ssahasra

compiler-rt/test/hwasan/TestCases/exported-tagged-global.c

@@ -4,6 +4,7 @@
 // RUN: %run %t
 // RUN: %clang_hwasan -O1 -mllvm --aarch64-enable-global-isel-at-O=1 %s -o %t
 // RUN: %run %t
+// REQUIRES: aarch64-target-arch
 
 static int global;