Using gradle it doesn't need ant to be installed anymore.
It's also much way faster than ant (on multiple builds),
on my computer is 25-50% faster than ant.

[ChangeLog][Android][androiddeployqt] Added Gradle support to build the
APK.

Change-Id: I3ed2c7215e38a43f5d5f62c3e6eedb601182e81a
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@digia.com>