QmlDevTools is really meant for host tools (the two only ones using this
being qmlmin in this repo and lupdate in qttools). qmake magic will take
care of bootstrapping them while x-building.

Change-Id: I29d921af483659d5455be0ad080dc1a88540c036
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>