The Whonix Makefile currently prevents build of Qubes template since it interferes with qubes-builder directives.
I have not yet identified the offending code within the Makefile or a possible solution as of yet.
As a stop-gap measure, I have deleted the Makefile to allow a build, which will cause a build-error if the Whonix repo is not committed. It would be nice to have an option to skip this test when building.
Will provide further details once I have Whonix 10 building and tested.