{nemu,npc}: inject mainargs to the bin file

* this removes the dependency of trm.c to keep the mainargs up-to-date

tools/insert-arg.py

@@ -0,0 +1,27 @@
+#!/usr/bin/env python3
+
+from sys import argv
+
+bin = argv[1]
+max_len = int(argv[2])
+placeholder = argv[3]
+mainargs = argv[4]
+
+if len(mainargs) >= max_len:
+    print("Error: mainargs should not be longer than {0} bytes\n".format( max_len))
+    exit(1)
+print("mainargs={0}".format(mainargs))
+
+fp = open(bin, 'r+b')
+data = fp.read()
+idx = data.find(str.encode(placeholder))
+if idx == -1:
+    print("Error: placeholder not found!\n")
+    exit(1)
+fp.seek(idx)
+mainargs_pad = str.encode(mainargs)+ ((max_len - len(mainargs)) * str.encode("\0"))
+if len(mainargs_pad) != max_len:
+    print("Error: len(mainargs_pad) != max_len\n")
+    exit(1)
+fp.write(mainargs_pad)
+fp.close()