C:\depot_tools\/git-cl

But in msys-git-1.8.0 it's:

C:\depot_tools\\git-cl

Handle either syntax correctly.

TBR=maruel@chromium.org
Review URL: https://codereview.chromium.org/11359074

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@166268 0039d316-1c4b-4281-b951-d872f2087c98