- incl some indicative fdt/extlinux/gpt info
- include full config and defconfig for each target
- mark the old .config file as legacy (it was always the last-target's config)
- fix: savedefconfig after build, not before (as target_map might change it)
- fix: some very old u-boots (2011, odroidc1) do not have `savedefconfig` at all, so make it optional
- fix: same for `.config` -- very old u-boots worked different (`boards.cfg`?)
7aeb48f172