cros-build: Add support for kevin (gru) and initial custom fw binary
This adds a custom build script for 'kevin' ('gru') that doesn't rely on Docker, as the cros_sdk for gru doesn't support the --nouse-image flag.
The script (cros_build/build_kevin.sh) takes care of downloading the sources and creating a sdk chroot appropriately. Once inside the chroot, to build the firmware run:
./kevin.sh setup ./kevin.sh checkout ./kevin.sh build
and the resulting firmware binary will be in cros_build/build/kevin.bin.
All the downloaded and generated files will be contained in the cros_build/build directory.
This also includes the custom firmware binary for kevin (firmware/kevin.bin), although it wasn't tested.
Signed-off-by: Ricardo Cañuelo firstname.lastname@example.org