QDB has to change to using Windows 10 for releases, because Windows 8.1
is no longer available for non-qt5 builds as a packaging platform in 5.9
branch.
Don't provision libusb on earlier Windows versions, since they don't
have a compatible compiler.
Change-Id: I771a24fcf208c4961483a39e51cb7d95f004ed55
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@qt.io>