reproduce (this is a W=1 build):
        # https://github.com/nunojsa/linux/commit/e18cc5c6741984280b0142955a2ea49bc6bf5484
        git remote add nsa https://github.com/nunojsa/linux
        git fetch --no-tags nsa b4/dev-iio-backend-add-debugfs
        git checkout e18cc5c6741984280b0142955a2ea49bc6bf5484
        # 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