reproduce (this is a W=1 build):
        # https://github.com/norov/linux/commit/a779e0e8dc6e9dc79210cb9a82a03d656f1e67d2
        git remote add norov https://github.com/norov/linux
        git fetch --no-tags norov find_and-v4
        git checkout a779e0e8dc6e9dc79210cb9a82a03d656f1e67d2
        # 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/block/null_blk/