SDKtool: Correctly handle mac ABIs

Task-number: QTCREATORBUG-11983

Change-Id: Id70bd18b1b5494db19adb9928277356c4d4a4688
Reviewed-by: Kai Koehne <kai.koehne@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>