Add -j option to gclient to run parallel updates

On a chromeos checkout, -j 10 brings down null sync time from 2 minutes to 16 seconds
Currently -j may break some assumptions about ordering of commands (which may be fine for some clients, but not all), so it's not on by default.

Review URL: http://codereview.chromium.org/1640001

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@44869 0039d316-1c4b-4281-b951-d872f2087c98
3 files changed