Debugger: Fix debugger startup on iOS

Task-number: QTCREATORBUG-12580
Change-Id: I8a2a38741719e8cf0b8a098eaa5d76eeb4bb1fb5
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>