This is done in gclient_eval, so we can remove all code
that deals with deps_os and hooks_os from gclient.
Bug: 839925
Change-Id: I491819207a712d62008ff010e313add87d22c937
Reviewed-on: https://chromium-review.googlesource.com/1058375
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Reviewed-by: Aaron Gable <agable@chromium.org>