[coreboot] Using cmos.default / nvramtool?

[Rafael Send]

Hi all-
I'm trying to set gfx_uma_size on my X210. From what I can tell, I need to
either use nvramcui / nvramtool to set this, or add a cmos.default file.

However, I'm not clear on how to do this correctly. If I just invoke
nvramtool, I'm told that this coreboot was built without selecting
"CONFIG_USE_OPTION_TABLE, which is not found in menuconfig.

How do I go about creating &using a proper cmos.layout file for my machine?

Thanks,
R