Building pi-kernel snap

Hello, I’m trying to build the pi-kernel snap for ubuntu core 20 for arm64… I started from pi branch, then I changed its snapcraft.yml to locally source instead of sourcing from git, to be able to change your internal reference MIRROR := ftpmaster.internal/ubuntu to MIRROR := in the Makefile, but, after proceeding for a bit, it fails with this error:

umount chroot/sys
umount chroot/proc
E: No packages found
E: No packages found
E: No packages found
echo "KIMGDEB: "
test -n "" || ( echo "Unable to extract KIMGDEB, exit"; false; )
Unable to extract KIMGDEB, exit
make: *** [Makefile.vmlinuz:75: version-check] Error 1
Failed to build 'kernel'.

Am I starting from the correct git repo? What can I do to proceed further?

My actual aim is to find a way to add few drivers in the kernel, like “virtio-blk”, “virtio-net”, “VGA” or “virtio-gpu”, to be able to run the resulting image in qemu-aarch64.

Thank you, Sandro