Ah cygwin...

Patch contributed by cmp@google.com

TBR=nsylvain
TEST=none
BUG=none

Review URL: http://codereview.chromium.org/125249

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@18613 0039d316-1c4b-4281-b951-d872f2087c98