reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic.git/commit/?id=625b37748a148e51ca888eac172f3a0a8f908ae9
        git remote add arnd-asm-generic https://git.kernel.org/pub/scm/linux/kernel/git/arnd/asm-generic.git
        git fetch --no-tags arnd-asm-generic master
        git checkout 625b37748a148e51ca888eac172f3a0a8f908ae9

        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # apt-get install llvm-dev

        # save the config file
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-14.2.0 ~/lkp-tests/kbuild/make.cross W=1 ARCH=powerpc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-14.2.0 ~/lkp-tests/kbuild/make.cross W=1 ARCH=powerpc 
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-14.2.0 ~/lkp-tests/kbuild/make.cross W=1 headers_install
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-14.2.0 ~/lkp-tests/kbuild/make.cross W=1 -C tools/testing/selftests