Switch gyp_chromium from third_party/python_26, which is gone, to
depot_tools/python276_bin.

BUG=335180
TEST=gclient runhooks works again on Cygwin
R=maruel@chromium.org

Review URL: https://codereview.chromium.org/141563007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@245705 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 245705