move the chroot stuff in its own file
move the chroot stuff in its own file

to make it more clearly what the basics things are that need to happen

hypriot/image-builder-bananapi,hypriot/image-builder-rpi,baseboxorg/image-builder-rpi,hypriot/image-builder-bananapi,hypriot/image-builder-rpi,baseboxorg/image-builder-rpi