[OE-core] Incorporating deploy artefacts from one multiconfig in another multiconfig

[Burton, Ross]

So I'd like to use multiconfig for a fairly typical host/container use
case.  I've a class which can be used to build packages from images in
a fairly simple manner, essential just taking files from DEPLOY_DIR
when creating a package:

core-image-minimal-package.bb:
do_install[depends] += "core-image-minimal:do_image_complete
virtual/kernel:do_deploy"
do_install () {
    install -d ${D}/var/lib/machines/
    install ${DEPLOY_DIR_IMAGE}/core-image-minimal-${MACHINE}.ext4
${D}/var/lib/machines/core-image-minimal.ext4
    install ${DEPLOY_DIR_IMAGE}/${KERNEL_IMAGETYPE}
${D}/var/lib/machines/${IMAGE_NAME}.${KERNEL_IMAGETYPE}
}

This part works fine, but the problem is straddling multiconfig boundaries...

I can't just add "core-image-minimal-package" to IMAGE_INSTALL because
it will build that for the current configuration.  I can't just add
"multiconfig:uos:core-image-minimal-package" because that will look
for a recipe with that name.  I've a rather ugly hack to call opkg
directly in a post-rootfs hook which sort of works.  Linking in bits
of the other configuration's deploy directory in a pre-rootfs hook and
extending IMAGE_INSTALL there almost works, apart from the rootfs code
then looks at the task dependencies to generate a pruned deploy dir,
which is missing the pieces I linked in.

I suspect this is now breaking new ground: the multiconfiguration
support lets you do builds but so far the artefact sharing hasn't
really been explored.  Has anyone dug further into this?

Ross