reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/zab/linux-rpdfs.git/commit/?id=e8e76da7ed715ef67ccc4436f4981a5b39983d9f
        git remote add zab-rpdfs https://git.kernel.org/pub/scm/linux/kernel/git/zab/linux-rpdfs.git
        git fetch --no-tags zab-rpdfs rpdfs-initial
        git checkout e8e76da7ed715ef67ccc4436f4981a5b39983d9f

        # 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