I've found myself automating Debian/kernel/boot loader/libs/app stack packages for some ARM hardware for which I'm an app developer. This is due to the outrageous situation of COM module vendors (and/or SoC manufacturers) thinking that kernel 3.0 and horribly ancient/unsupported/unpatched userlands are acceptable in 2014/2015.
I run our .deb builds (and final debootstrap) in a bunch of docker containers, given that xapt/debcross toolchain has some stuff that, although these are awesome in themselves, still have some quirks when building stuff with awkward/complex dependencies and require a lot of hand-holding normally. So dockerizing the build env makes my life easier (some of it still has to be done from arm native chroot via qemu+binfmts). I use Jenkins to automate and integrate with the rest of our build tools but make files work too.
The /etc/passed et. al. copying from host is definitely the wrong thing to do in my circumstances as well; it's curious the various failure modes chroot builds can have.