Manual Build

At least on Ubuntu 14.10, it is possible to use the prepackaged `gcc-arm-linux-gnueabihf` toolchain to build uboot, linux, and busybox to prepare a very small working image with minimal source customization.

If Buildroot is too opaque, and debootstrap is too big, have a look at https://github.com/ckuethe/usbarmory/tree/master/tinyimage

See also https://eewiki.net/display/linuxonarm/i.MX53+Quick+Start