reproduce (this is a W=1 build):
        # https://github.com/zen-kernel/zen-kernel/commit/0bb79c27b3df116c04124af95548021cfae9dc89
        git remote add zen https://github.com/zen-kernel/zen-kernel
        git fetch --no-tags zen 7.3/mglru-fg-v4
        git checkout 0bb79c27b3df116c04124af95548021cfae9dc89

        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=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash