reproduce (this is a W=1 build):
        # https://github.com/nunojsa/linux/commit/4120536adfc0bc741c466d38ae50ffb9760576e3
        git remote add nsa https://github.com/nunojsa/linux
        git fetch --no-tags nsa b4/dev-iio-backend-add-debugfs
        git checkout 4120536adfc0bc741c466d38ae50ffb9760576e3
        # 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 drivers/iio/adc/