[HWASan] comment why hwasan_symbolize_stack_uas is arm64 only

Author: fmayer

compiler-rt/test/hwasan/TestCases/hwasan_symbolize_stack_uas.cpp

@@ -1,7 +1,8 @@
 // RUN: %clang_hwasan -Wl,--build-id -g %s -o %t
 // RUN: %env_hwasan_opts=symbolize=0 not %run %t 2>&1 | hwasan_symbolize --symbols $(dirname %t) --index | FileCheck %s
 
-// TODO: find out why this fails on sanitizer-x86_64-linux-qemu bot
+// This doesn't work on X86, because that uses instrument-with-calls which
+// disables frame records.
 // REQUIRES: aarch64-target-arch
 
 #include <sanitizer/hwasan_interface.h>