tools/mpy-tool: Make work if run from another directory.

By making sure we don't add relative paths to sys.path.

tools/mpy-tool.py

@@ -45,7 +45,7 @@ import sys
 import struct
 from collections import namedtuple
 
-sys.path.append('../py')
+sys.path.append(sys.path[0] + '/../py')
 import makeqstrdata as qstrutil
 
 class FreezeError(Exception):