reproduce (this is a W=1 build):
        # https://github.com/plbossart/sound/commit/2ac8e1bbf1ec8eeb41f02e27879939321999656b
        git remote add plbossart-sound https://github.com/plbossart/sound
        git fetch --no-tags plbossart-sound sdw/sdca-function-devices
        git checkout 2ac8e1bbf1ec8eeb41f02e27879939321999656b
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash