reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git/commit/?id=3499375209ca839a741e775d579f8bb9b85529d5
        git remote add jic23-iio https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git
        git fetch --no-tags jic23-iio togreg
        git checkout 3499375209ca839a741e775d579f8bb9b85529d5

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=um olddefconfig
        make W=1 O=build_dir ARCH=um SHELL=/bin/bash