Remove cygwin support from buildbot_pnacl_toolchain.py
Remove cygwin support from buildbot_pnacl_toolchain.py

Remove some custom munging that existed to support the mixing of cygwin and
Windows native python. This change is not intended to remove all cygwin
support from the build infrastructure, just from this file to facilitate
further changes.

R=dyen@chromium.org
BUG= https://code.google.com/p/nativeclient/issues/detail?id=3473

Review URL: https://codereview.chromium.org/791183003

git-svn-id: 721b910a23eff8a86f00c8fd261a7587cddf18f8@14196 fcba33aa-ac0c-11dd-b9e7-8d5594d729c2

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