avoid deleting the lib/empty file

Makefile

@@ -48,7 +48,7 @@ clean:
 	rm -f crt/*.o
 	rm -f $(OBJS)
 	rm -f $(LOBJS)
-	rm -f $(ALL_LIBS) lib/*
+	rm -f $(ALL_LIBS) lib/*.[ao] lib/*.so
 	rm -f $(ALL_TOOLS)
 	rm -f $(GENH) 
 	rm -f include/bits