WIP: Enable boot image generation
Relates to: librem5-devkit-tools#10
Now that the boot image can be generated (!93), do it for the devkit board.
This is WIP: since the requirements to merge this safely are not met yet.
Among other things, it depends on:
having the download/flash scripts in Librem5/librem5-devkit-tools> be able to process
both single-image andmulti-image builds (librem5-devkit-tools!60)
- having the UUU scripts in Librem5/librem5-devkit-tools> be able to flash the U-boot and configure the eMMC to boot from the correct partition (librem5-devkit-tools!44)
- building a U-boot using the purism/librem5 board, with the env located in the boot partition
- provide an utility capable of safely updating the bootloader from within Linux (copy new boot image to the currently inactive MMC boot hwpart, copy the previous U-boot env from the active hwpart, and activate the hwpart where the new boot firmware was just written)