Yes. I guess KVM requires to run the gitian host on a physical machine, although VMWare can emulate KVM in a VM.
wumpus: lxc isn't working for me, and I am not using a vm as the host (thankfully)
jonasschnelli: right, there is some CPU bit, that if you VM environment supports it, and it is enabled, can allow for nested virtualization :)
but I'm not aware of anyone using it in that way, it seems awfully specific
Gavin had a very strange setup at some point where he built in vmware w/ Ubuntu VM directly. But the problem of using an 'alternative' setup is that it may have differences that result in different executables
(although this is mostly solved with the depends system, there is no reliance on any OS-shipped libraries)