Packer qemu builder

Run packer into docker container with qemu to build qcow2 gentoo os

use

run make up to start container and build qcow2

iso checksum

iso_checksum_url": "http://distfiles.gentoo.org/releases/amd64/autobuilds/current-install-amd64-minimal/install-amd64-minimal-{{user version}}.iso.DIGESTS