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 extron
        git checkout 64403b1cf011de24701c54aa5c71fa3897b3a920
        # 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/cec/usb/extron-da-hd-4k-plus/