build_image: Include {ignition,bootengine} in {packages,licenses}.txt
build_image: Include {ignition,bootengine} in {packages,licenses}.txt

They're not in the root fs, but they are in the initramfs.  Handle this
by augmenting the package list with packages that are both

- build dependencies of coreos-kernel, and
- configured to cause rebuilds of coreos-kernel when their sub-slot
  changes.

glevand/coreos--scripts,coreos/scripts,coreos/scripts,glevand/coreos--scripts