Yes, you could, but it’s not as simple as modifying the config.librem15v3 because of the following reasons :
- The script would checkout a clean clone of that git repo and copy the config file from there, so your changes would be ignored anyway
- Modifying the config file manually is not supported by coreboot, when you type ‘make’, it will regenerate the config file somehow, and may or may not override your settings
- Enabling one option could create new config options that need to be set which aren’t even listed in the config file
- The script verifies that the build has the expected hash, if you change a single thing in the config, the hash won’t match and the script will think that some error happened which caused a corrupted build and it won’t ask you to flash it and will show you an error.
What you could do however is that you would first build it normally, then after it’s done, go into the coreboot directory and do ‘make menuconfig’. In the menu, go to payload and change the payload, then save config and exit the menuconfig. Then when you do ‘make’, it will compile coreboot with your new options (grub). After that, you need to create a serial_number.txt file and put your machine’s serial number in it and use cbfstool to insert the serial_number.txt file into the resulting coreboot.rom image (otherwise, when you boot, dmidecode will report ‘unknown serial number’)… the method and arguments to do that are in the script file, then you’d need to run the me_cleaner script on the resulting build/coreboot.rom file (required arguments are in the build script). then you need to flash it manually (arguments to flashrom are in the build script). Once it’s flashed, and that’s the big issue, you would need to cross your fingers, reboot and HOPE that it will boot into your machine. Because if the grub config file (which also needs to be provided and embeded in the coreboot.rom file) is somehow wrong and grub doesn’t detect your drive (because you made a typo in the partition name, or something… anything…), then you can’t boot your machine. If you can’t boot your machine, you won’t be able to fix the grub config file and re-flash it. so you would need to buy a hardware flasher, open the laptop and flash a known-working coreboot image back into your flash so you could boot it again.
so in short, yes, you can do it, but it’s not as simple as changing the config file. I don’t even know if you could have grub boot from your usb, or maybe you can enter a ‘grub shell’ and manually type the commands to make it boot from a usb stick so you could boot into a live USB and restore your system… but that also assumes that the graphics are initialized, which is something that SeaBIOS does, and I don’t think that grub does that, so you might also need to edit the coreboot configuration to tell it to run the VGA Option ROM and to initialize the GPU, otherwise grub might appear but the screen is off and you can’t see anything…
All these complications are why the script checks the hash and makes sure the image it builds and flashes is a known working image. If you have, or are willing to buy an external flasher and play with it until it works for you, then feel free to do so. I am however too busy with other tasks to try and test/confirm that every payload would work (I know that MrChromeBox has unofficial builds that use TianoCore as the payload, I’m not sure if he released those anywhere though).