'fetch chromium' will fail if the build dependencies are not already installed
on the host machine, because it runs 'gclient sync' which, by default, will run
hooks that will try to run build/gyp_chromium (which will then fail).

This introduces a --nohooks option that solve the problem by allowing the
user to do the following:

  1) fetch --nohooks <recipe>
  2) src/build/install-build-deps.sh
  3) fetch <recipe>

BUG=325795
TEST=Run 'fetch --nohooks chromium' in a temporary 'clean' chroot directory.
R=maruel@chromium.org,jochen@chromium.org,scottmg@chromium.org,agable@chromium.org

Review URL: https://codereview.chromium.org/106403003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@240680 0039d316-1c4b-4281-b951-d872f2087c98