Wait for exit-code thread to terminate before terminating main.

runtime/bin/process.h

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #ifndef BIN_PROCESS_H_
 #define BIN_PROCESS_H_
 
 #include "bin/builtin.h"
 #include "platform/globals.h"
 
@@ skipping 13 matching lines @@
                    intptr_t* exit_handler,
                    char* os_error_message,
                    int os_error_message_len);
 
   // Kill a process with a given pid.
   static bool Kill(intptr_t id);
 
   // Indicate that the process with the given pid has exited.
   static void Exit(intptr_t id);
 
+  // Terminate the exit code handler thread. Does not return before
+  // the thread has terminated.
+  static void TerminateExitCodeHandler();
+
   DISALLOW_ALLOCATION();
   DISALLOW_IMPLICIT_CONSTRUCTORS(Process);
 };
 
 #endif  // BIN_PROCESS_H_