reproduce (this is a W=1 build):
        # https://github.com/jimc/linux/commit/6ee79369c7f2a0d78a4087eb30f12b2bae53f162
        git remote add jimc https://github.com/jimc/linux.git
        git fetch --no-tags jimc dd-classmaps-v13-akpm
        git checkout 6ee79369c7f2a0d78a4087eb30f12b2bae53f162

        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=xtensa olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=xtensa SHELL=/bin/bash lib/