Comment 13 for bug 1808056

I've put together an update for flash-kernel that handles booting an uncompressed image (to support existing arm64 installs), a self-compressed image (to support existing armhf installs), and a gzip'd image (to support the proposed format). It assumes the kernel is called "vmlinuz" in all cases (because that's currently the case, and I presume will continue to be the case in future).

Just finishing up testing today, but I've already confirmed it works on pi2, pi3, and pi3+ with all (supported) kernel cases - just cm3 and cm3+ to go. The update also switches the pi2 case to using the same boot-script as all the rest. I'll ping Lukasz for a review when everything's confirmed as working.