Build a generic qcow2 image. 🔼

Had a request for a VHD, but a qcow2 would be better.

I'm in the middle of updating my Devuan OS install script, which builds to a qcow2 for testing.  So I can add this to that.

reported=2020-02-12 21:48:48

reporter=onefang

priority=normal

category=Feature

severity=feature