make the MinGW build of setup-qt work for non-admin users

We now embed a manifest in the MinGW build of qbs-setup-qt.

Task-number: QBS-275
Change-Id: Id984987a57850c0aed23a7c6852c15e447a2f096
Reviewed-by: Christian Kandeler <christian.kandeler@digia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>