Android: Skip tools built for target architecture

Android apps require packaging to be usable, so they need to be
built individually, not as part of the subdirs build. The build would
fail during make install due to this.

Task-number: QTBUG-34023
Change-Id: If7627dcdc15334f82c454c6a2a19501fcc6bc970
Reviewed-by: Paul Olav Tvete <paul.tvete@digia.com>