Automate the fetching of ics-openvpn-stripped from an already checked out ics-openvpn-upstream branch

Given a location of ics-openvpn-stripped, we should be able to fecth its sources and process them accordingly before building, as a dependency of the android "build" task.

It should be something like build.dependsOn fetchIcsOpenvpnStripped, but properly situated in a build.gradle file.

(from redmine: created on 2014-05-27, closed on 2014-05-28)