Prepend jinja2 path for hermeticity.

mojo/nacl/generator/generate_nacl_bindings.py

 #!/usr/bin/python
 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # pylint: disable=W0104,W0106,F0401,R0201
 
 import errno
 import optparse
 import os.path
@@ skipping 11 matching lines @@
   also be "above" this file)."""
   path = _ScriptDir()
   while True:
     path, tail = os.path.split(path)
     assert tail
     if tail == dirname:
       return path
 
 
 def _AddThirdPartyImportPath():
-  sys.path.append(os.path.join(_GetDirAbove('mojo'), 'third_party'))
+  sys.path.insert(0, os.path.join(_GetDirAbove('mojo'), 'third_party'))
 
 
 _AddThirdPartyImportPath()
 import jinja2
 
 loader = jinja2.FileSystemLoader(_ScriptDir())
 jinja_env = jinja2.Environment(loader=loader, keep_trailing_newline=True)
 
 
 # Accumulate lines of code with varying levels of indentation.
@@ skipping 455 matching lines @@
   GenerateMojoSyscall(mojo.functions, out)
 
   out = OutFile(options.out_dir, 'mojo_irt.h')
   GenerateMojoIrtHeader(mojo.functions, out)
 
   out = OutFile(options.out_dir, 'mojo_irt.c')
   GenerateMojoIrtImplementation(mojo.functions, out)
 
 if __name__ == '__main__':
   main(sys.argv[1:])