reproduce (this is a W=1 build):
        # https://github.com/frank-w/BPI-R2-4.14/commit/1a140ff79b8bf1a9f5ddb079b6e2b404929f0a36
        git remote add frank-w-bpi-r2-4.14 https://github.com/frank-w/BPI-R2-4.14
        git fetch --no-tags frank-w-bpi-r2-4.14 7.1-rc
        git checkout 1a140ff79b8bf1a9f5ddb079b6e2b404929f0a36

        # install powerpc cross compiling tool for clang build
        # apt-get install binutils-powerpc-linux-gnu
        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=$HOME/0day COMPILER=clang-16 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-16 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash