[scudo] Fix running tests under hwasan.

[eugenis]

Summary

When built with hwasan, assume that the target architecture does not
support TBI. HWASan uses that byte for its own purpose, and changing it
breaks things.

compiler-rt/lib/scudo/standalone/memtag.h

 
 namespace scudo {
 
 #if (__clang_major__ >= 12 && defined(__aarch64__)) || defined(SCUDO_FUZZ)
 
 // We assume that Top-Byte Ignore is enabled if the architecture supports memory
 // tagging. Not all operating systems enable TBI, so we only claim architectural
 // support for memory tagging if the operating system enables TBI.
-#if SCUDO_LINUX && !defined(SCUDO_DISABLE_TBI)
+// HWASan uses the top byte for its own purpose and Scudo should not touch it.
+#if SCUDO_LINUX && !defined(SCUDO_DISABLE_TBI) &&                              \
+    !__has_feature(hwaddress_sanitizer)
 inline constexpr bool archSupportsMemoryTagging() { return true; }
 #else
 inline constexpr bool archSupportsMemoryTagging() { return false; }
 #endif
 
 inline constexpr uptr archMemoryTagGranuleSize() { return 16; }
 
 inline uptr untagPointer(uptr Ptr) { return Ptr & ((1ULL << 56) - 1); }