reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # install powerpc cross compiling tool for clang build
        # apt-get install binutils-powerpc64-linux-gnu
        git remote add drm-misc git://anongit.freedesktop.org/drm/drm-misc
        git fetch drm-misc drm-misc-next
        git checkout drm-misc/drm-misc-next
        b4 shazam https://lore.kernel.org/r/a8f71940221fb085b8767f8123f496c9b36b22cc.1704276309.git.jani.nikula@intel.com
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-18 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-18 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash drivers/gpu/drm/bridge/synopsys/