reproduce (this is a W=1 build):
        # https://github.com/jimc/linux/commit/02e60097f7e9bc1e34612bfdb35fb231d25bd52e
        git remote add jimc https://github.com/jimc/linux.git
        git fetch --no-tags jimc dd-classmap-fix-v4h
        git checkout 02e60097f7e9bc1e34612bfdb35fb231d25bd52e
        # 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