By launching an installer with Start-Process and -Wait,
we make sure no handles are left holding on to the
installer when we try to delete it at cleanup.
Change-Id: Ic9b700ea1ce9e70089ba4cb7e91d9765ca976333
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@qt.io>