This prevents the 'cordova build android' process from blowing up on this step if you assign the GDK as the target and want to rebuild via the CLI.
close#100
Since cordova-cli calls the check_req library run() method, we do not
want to always console.log on success in there (not usually a useful side
effect).
This eliminates the use of shelljs.exec's sync mode, which is the source
of the filehandle leaks that can cause EMFILE on OSX, and are
CPU-intensive everywhere.
Tested locally, needs poking before it gets released.