Allow colors in arc commands on windows
This dosen't work on cmd since this must have been disabled for a reason
but git for windows is basicaly like git on linux so there is no reason
for color to be disabled on bash type programes.
This allows colors in arc so it is not blank, makes it colorful.
Reviewers: greg, demon, Luke081515, mmodell
Reviewed By: Luke081515, mmodell
Differential Revision: https://phabricator.wikimedia.org/D222