[HWASan] Fixed minor AArch64/GCC build error.
Fixed buildbot clang-cmake-aarch64-lld by ensuring clang-only features
are guarded by clang-only #defines.
@@ -100,7 +100,11 @@ __hwasan_tag_mismatch:
.Lfunc_end0:
.size __hwasan_tag_mismatch, .Lfunc_end0-__hwasan_tag_mismatch
+// Address significance tables cannot be emitted on gcc. Some buildbots
+// (clang-cmake-aarch64-lld) use gcc to build compiler-rt.
+#if __clang__
.addrsig
+#endif // __clang__
#endif // defined(__aarch64__)
