#123 Add some chromebooks with U-Boot as a payload

I spent about a week to explore U-Boot support as a side project. A lot of things here, also see the commit messages. Mainly:

• Fixes U-Boot-libre release script reproducability issues
• Adds a v2022.07 U-Boot-libre release (supersedes #121)
• Makes U-Boot download script prepare trees per-board
• Makes it more in-line with the coreboot scripts
• Adds support for using U-Boot as a coreboot payload
• Adds config modify scripts for U-Boot
• Some build system fixes and improvements
• Initial support for Gru, Veyron, Nyan chromebooks with U-Boot

I was going to do this for gru-kevin only, but after doing that the rest looked like low hanging fruit so I added untested configs for them as well. I also tried configs for peach-pit, snow, spring but they need non-free blobs, may be useful for osbmk.

Most things work on gru-kevin, but it doesn't power-off properly, don't know why. U-Boot branding is mostly still U-Boot except for a libreboot mention in the version. There's also still important user-invisible stuff that's missing, like SMBIOS sysinfo, integration between coreboot and U-Boot, possible firmware layout changes, and who knows what.

I guess it also needs updates for the dependency install scripts, but I'm too tired to do that especially since I have them all already installed. U-Boot docs has a dependencies list that you might want to reference.

I may not get more time to work on this, mostly throwing code over the fence. Enjoy!

Can you add the extra boards too? I see you have the other branches for this in your lbmk repo.

I'm going ahead with a planned osboot/libreboot merger, so those other boards are fine to put in lbmk. I mean the ones that you say "may be useful for osbmk".

osboot is being scrapped soon, and all of it will be integrated into libreboot. The official libreboot policy will be changed to match the osboot one, accordingly. This is happening as part of the next release.

More info:

https://libreboot.org/news/libreboot20220710.html#planned-osbootlibreboot-merger

I've pushed that branch to this one, and deleted that one.