the platform/initramfs/ code atm is not easily testable ... you have to set up a device and do a full build in order to find out if your one line change to the init code was junk :).

i posted a CL to improve things a bit:
  https://chromium-review.googlesource.com/266443

just going to outline the goals for the test logic so we can have an end in sight.
(0) we can assume we'll have an existing sysroot for a board -- i.e. someone already ran `./build_packages` for us
(1) build the initramfs for each target
(2) build the kernel with the right settings locally for each target and merge in the initramfs
(3) create a simple raw disk image with the right partition layout
(3a) no need to fully populate the contents of the disk image -- TBD what exactly will be dumped in here
(4) boot the system in qemu, either directly given the kernel, or indirectly given the disk image
(5) all testing from there on out is manual review
(5b) automation to check the results would be nice if feasible, but can punt till later