[tsan] Disable Trace.MemoryAccessSize on Mac

According to comments at https://reviews.llvm.org/D107911,
Trace.MemoryAccessSize fails on Mac buildbots.
Because this test is newly introduced, and is the only user of the code
added in that patch, disable the test on Mac till the problem is
resolved.

Differential Revision: https://reviews.llvm.org/D108294

compiler-rt/lib/tsan/tests/unit/tsan_trace_test.cpp

@@ -76,7 +76,14 @@ TEST(Trace, RestoreAccess) {
   run_in_thread(Thread::Func);
 }
 
-TEST(Trace, MemoryAccessSize) {
+#if SANITIZER_MAC
+// Trace.MemoryAccessSize is currently failing on Mac.
+// See https://reviews.llvm.org/D107911 for more details.
+#  define MAYBE_MemoryAccessSize DISABLED_MemoryAccessSize
+#else
+#  define MAYBE_MemoryAccessSize MemoryAccessSize
+#endif
+TEST(Trace, MAYBE_MemoryAccessSize) {
   struct Thread {
     struct Params {
       uptr access_size, offset, size;