Support changing SeaBIOS boot order about skulls

[wlhlm]

OK, I can confirm that changing the boot order generally works. I've opted for a different method of installing the bootorder file: instead of using the Kconfig option SEABIOS_BOOTORDER_FILE, I manually modified the coreboot image after the build using the cbfstool from coreboot-utils.

The coreboot image from the release page is truncated to 4MiB and doesn't work with cbfs, so I have to manually build coreboot to get the full image.

$ git clone "https://github.com/merge/skulls"
$ cd skulls/x230
$ ./build.sh
$ cp build/build/coreboot.rom ./

Then I create a bootorder file with the following contents:

/pci@i0cf8/*@1f,2/drive@2/disk@0
/pci@i0cf8/*@1f,2/drive@0/disk@0
/rom@img/nvramcui

Then I include it in the coreboot ROM and truncate the ROM to 4MiB:

$ cbfstool coreboot.rom add -f bootorder -n bootorder -t raw
$ dd if=coreboot.rom of=coreboot.truncated.rom bs=1M skip=8

coreboot.truncated.rom is then flashed onto the x230.

[merge]

I'd like to have this integrated into x230_skulls.sh as one simple option to switch to the mSATA being the default. This will involve:

• adding cbfstool to the util directory, as self-contained as possible.

If the mSATA option is chosen:

• build it as part of x230_skulls.sh (similar to ifdtool used in external_install_bottom.sh)
• generate the bootorder file you provided directly from the script
• let cbfstool add it to the output/x230_coreboot_seabios_xxx_12M_prepared.rom file we already generate

Feel free to do it and create a pull request. I might look into it too if time permits.

[merge]

purism already does that, see https://source.puri.sm/coreboot/releases/blob/master/update_coreboot.sh

we could actually use quite some more from this script too.