This CL adds the recursive deps of buildtools to the top-level DEPS which is now
mandatory due to the recent changes in the buildtools repo.

R=machenbach@chromium.org
CC=yangguo@chromium.org,sergiyb@chromium.org

Bug: chromium:930050
Change-Id: I0eba652078de75fb22942dd2f5434cd3bd65ada1
Reviewed-on: https://chromium-review.googlesource.com/c/1466302Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Tamer Tas <tmrts@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59519}