kernel source : compile from a ubuntu (gnu/linux) system : possible?

[mayuresh%kathe.in@localhost <mayuresh%kathe.in@localhost>]

i've heard about the impressive portability of the netbsd system, especially it's kernel.
i've also heard that it's possible to cross-compile the whole system for a different target 'isa'.
so, i wondered if it's possible to compile the netbsd kernel (only) source from a gnu/linux system like ubuntu. i don't expect to "run" the kernel, just to modify the source (primarily working on updating from older 'c' to c99 and secondarily to identify and patch code issues with security) and compile to test whether everything goes through and then submit the patches.
all this because netbsd won't support all of my hardware and also incapability to use virtualisation.
thanks.