Hi,
I am trying to build payload "seabios" as I am using freebsd kernel.
As per - http://www.coreboot.org/SeaBIOS
Probably the easiest way to use SeaBIOS as coreboot payload is to simply use the coreboot build process, which downloads and builds SeaBIOS as payload by default nowadays. You just have to run the following in your coreboot checkout:
$ make menuconfig
$ make