Make sure we are using gradle 2.x

Make sure we are using gradle 2.x

Google is playing with my nerves! Android SDK Tools v24.0.0 set gradle
1.x by default, then in v24.0.1 they've switched to gradle 2.x.
Incredibly, a few days later they're released v24.0.2 and again they've
switched back to gradle 1.x as the default gradle version. Thought, when
a project is opened in Android Studio, Android Studio switches to gradle
2.x. We'll do the same thing in androiddeployqt.

Change-Id: Id5ca3f94a96b230cbb6af410bccf292d53f9ea5b
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@theqtcompany.com>