reproduce (this is a W=1 build):
        # https://github.com/Freescale/linux-fslc/commit/16b65085d4d93242942e510c861a445167acc4e6
        git remote add freescale-fslc https://github.com/Freescale/linux-fslc
        git fetch --no-tags freescale-fslc 6.1-2.2.x-imx
        git checkout 16b65085d4d93242942e510c861a445167acc4e6
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=um olddefconfig
        make W=1 O=build_dir ARCH=um SHELL=/bin/bash