[HWASAN] Added empty WordIsPoisoned for LSAN support.

[kstoimenov]

Summary

Currently it is just an empty implementation to allow the project to link.

[kstoimenov]

Added fixme.

compiler-rt/lib/hwasan/hwasan_poisoning.cpp

 
 uptr TagMemory(uptr p, uptr size, tag_t tag) {
   uptr start = RoundDownTo(p, kShadowAlignment);
   uptr end = RoundUpTo(p + size, kShadowAlignment);
   return TagMemoryAligned(start, end - start, tag);
 }
 
 }  // namespace __hwasan
+
+// --- Implementation of LSan-specific functions --- {{{1
+namespace __lsan {
+bool WordIsPoisoned(uptr addr) {
+  // Fixme: implement actual tag checking.
+  return false;
+}
+}  // namespace __lsan