Fix debian installer
After this MR, the only thing blocking debian-installer from building is that trisquel-keyring-udeb is missing from our debian-installer/main repo.
I used a local repo to provide trisquel-keyring-udeb and was able to build mini.iso. I then tried using mini.iso to install Trisquel. The install failed because debootstrap-udeb is missing from our debian-installer/main repo.
@ruben Please definitely build
and then almost certainly build
and then maybe build