Setup

Install the required packages to build the system. sudo apt-get install git build-essential ncurses-dev kpartx

Building

git clone --depth 1 git://github.com/NextThingCo/rpi-buildroot.git
cd rpi-buildroot
make stak_raspi_hwtest_defconfig
make nconfig         # if you want to add packages or fiddle around with it
                     # the Stak packages currently need to be enabled or they won't get included
make                 # build (NOTICE: Don't use the **-j** switch, it's set to auto-detect)

Create SD Card IMG

SD card image is created automagically as part of the build process. You can find the result
    at output/images/rpi-sdimg.img