which is particularly helpful when one is using `gclient sync' on a platform
that does not have /bin/bash (ie. it's installed in another location or not
present at all), since the hooks are automatically added to the git
checkouts.

While here, just `exec' the scripts directly instead of invoking another
shell by hand and remove the redundant `exit 0' lines.

R=cmp@chromium.org,dpranke@chromium.org,szager@chromium.org

Review URL: https://chromiumcodereview.appspot.com/19278004

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@214181 0039d316-1c4b-4281-b951-d872f2087c98