A follow up task of T298.
As of Whonix 11, there is no difference between --target root and --target qubes.
For Whonix 12, we will need a way to distinguish VM builds, i.e. also Qubes builds from physical isolation builds. (For T296 and perhaps in future other things as well.)
It could be done for Whonix 11 already, but there is no rush. Doesn't matter.