Within the VM, the guix that is being used is Guix's "guix" package
(gnu/packages/package-management.scm), which will not have any knowledge
of your packages or any other modifications in your git branch.

One thing you could do is add your packages to the vm config's
"package" field so that they are installed system-wide in the VM.

Another, untested, idea might be to map your git checkout into your
vm user's ~/.config/guix/latest

`~Eric