Fix memory leak in ManagedStatic

[aratajew]

Summary

ManagedStaticMutex is allocated once we call getManagedStaticMutex, but it is nowhere deallocated.

[dblaikie]

Generally (especially bounded) memory allocation that remains reachable but is not allocated isn't considered a leak, as such.

I believe this code as-is is intentional.

[amaiorano]

This comment was removed by amaiorano.

lib/Support/ManagedStatic.cpp

 
 /// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
 void llvm::llvm_shutdown() {
-  MutexGuard Lock(*getManagedStaticMutex());
+  {
+    MutexGuard Lock(*getManagedStaticMutex());
+
+    while (StaticList)
+      StaticList->destroy();
+  }
 
-  while (StaticList)
-    StaticList->destroy();
+  delete ManagedStaticMutex;
+  ManagedStaticMutex = nullptr;
 }