[d8] reset global handle on exit.

R=neis@chromium.org
BUG=v8:4887
LOG=N

Review URL: https://codereview.chromium.org/1857263002

Cr-Commit-Position: refs/heads/master@{#35270}

src/d8.cc

@@ -2478,6 +2478,9 @@ int Shell::Main(int argc, char* argv[]) {
 
     // Shut down contexts and collect garbage.
     evaluation_context_.Reset();
+#ifndef V8_SHARED
+    stringify_function_.Reset();
+#endif  // !V8_SHARED
     CollectGarbage(isolate);
   }
   OnExit(isolate);