Modifies platform_tools.py to be compatible with python 2.6
Modifies platform_tools.py to be compatible with python 2.6

The architecture dictionary used dictionary comprehensions to generate
itself, this change modifies it so machines running versions of python
lower than 2.7 will still work.

R=jvoung@chromium.org, jvoung@google.com
BUG=

Review URL: https://codereview.chromium.org/133273014

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@12614 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client,sbc100/native_client