Resending because I forgot to mail it to the list:
Hello Antony,
Firstly, the quoted message matches the one added by CB:28382 [1], which makes me think you are not using 4.8.1, but master instead. This is not the primary issue, though it is worth noting.
With regard to the message you mentioned, its purpose is to warn unsuspecting people against flashing a *complete* coreboot.rom when it lacks an IFD (Intel Flash Descriptor). AFAIK, most modern systems will fail to function properly without it. That does not mean the image is unbootable, but it is not usable on its own.
If you want to flash it to a flash chip, your flasher software must be able to write only to the BIOS region (defined by the IFD). flashrom [2] is capable of doing so, with the IFD or layout options. The former uses the existing flash chip contents to determine the region to flash.
Another option is to extract the IFD and other regions from the flash chip, add them to coreboot (either using coreboot's Kconfig options or manually splicing the files) and flash the resulting, complete image. I do not recommend this unless absolutely necessary (it rewrites the whole flash chip instead of the desired region, which is more error-prone).
Best regards,
Angel Pons Pons
[1]: https://review.coreboot.org/c/coreboot/+/28382 [2]: https://www.flashrom.org/Flashrom (I do not know about Chromium flashrom's capabilities)