bug#66220: VM root file system has no label

[Ricardo Wurmus]

When building a Guix System VM (qcow2) image from an operating system
file containing the following file systems

  (file-systems (append
                 (list (file-system
                         (device (file-system-label "my-root"))
                         (mount-point "/")
                         (type "ext4")))
                 %base-file-systems))

the resulting image will not have the label “my-root”.  When booting the
virtual machine and reconfiguring with the configuration file (as saved
by “--save-provenance”) Guix will complain about the fact that there is
no disk with the given label.

-- 
Ricardo