To build your kernel you need to have a file in the top level directory that contains the following configuration variables (with the defaults that I use to build my dna kernel as an example):
N_CORES=4 VERSION=crpalmer-1.1.20 CROSS_COMPILE="ccache /opt/toolchains/linaro-4.7/bin/arm-eabi-" HOST_CC="ccache gcc" LOCAL_BUILD_DIR=dna TARGET_DIR=~/dna/updates SYSTEM_PARTITION="/dev/block/mmcblk0p32" BANNER= FLASH_BOOT='package_extract_file("boot.img", "/tmp/boot.img"), write_raw_image("/tmp/boot.img", "boot")'
The file is "crpalmer-build-config". In the LOCAL_BUILD_DIR you must have the following files:
initrd.img bootimg.cfg