init: init nachos hw01, should pass jenkins os_group_20_hw job but fail on os_group_20_ta job

code/threads/main.h

@@ -0,0 +1,19 @@
+// main.h 
+//	This file defines the Nachos global variables
+//
+// Copyright (c) 1992-1996 The Regents of the University of California.
+// All rights reserved.  See copyright.h for copyright notice and limitation 
+// of liability and disclaimer of warranty provisions.
+
+#ifndef MAIN_H
+#define MAIN_H
+
+#include "copyright.h"
+#include "debug.h"
+#include "kernel.h"
+
+extern Kernel *kernel;
+extern Debug *debug;
+
+#endif // MAIN_H
+