reproduce (this is a W=1 build):
        git remote add hverkuil-media-tree git://linuxtv.org/hverkuil/media_tree.git
        git fetch --no-tags hverkuil-media-tree outreachy-vivid-v6.7
        git checkout 4bc7849217d6c105cb59d78e9995b8e129f0deaf
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/media/test-drivers/vivid/