[perf] Fix a data race in the PerfJITEventListener

Concurrent JIT compilation + PerfJITEventListener triggers tsan error

Reviewed By: cota

Differential Revision: https://reviews.llvm.org/D104977

lib/ExecutionEngine/PerfJITEvents/PerfJITEventListener.cpp

@@ -284,6 +284,9 @@ void PerfJITEventListener::notifyObjectLoaded(
     NotifyCode(Name, *AddrOrErr, Size);
   }
 
+  // avoid races with writes
+  std::lock_guard<sys::Mutex> Guard(Mutex);
+
   Dumpstream->flush();
 }