While using --jobs, empty lines are adding a lot of noise.

An example output would look like:

>gclient sync --jobs=10
1>
3>
4>
6>
5>
7>
5>
5>________ running 'git clone ...'
Review URL: http://codereview.chromium.org/7101012

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@87542 0039d316-1c4b-4281-b951-d872f2087c98