reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # https://github.com/linuxppc/linux/commit/b5af3438997c07a6c4f5f3bf3a00f2172f019759
        git remote add linuxppc https://github.com/linuxppc/linux
        git fetch --no-tags linuxppc merge-test
        git checkout b5af3438997c07a6c4f5f3bf3a00f2172f019759
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-13.2.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-13.2.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash arch/powerpc/kernel/