reproduce (this is a W=1 build):
        git remote add kees https://git.kernel.org/pub/scm/linux/kernel/git/kees/linux.git
        git fetch kees for-next/hardening
        git checkout kees/for-next/hardening
        b4 shazam https://lore.kernel.org/r/cd09427148a0c4718b46029c9e806f9dc1622f9b.1794425425.git.alx@kernel.org

        # install s390 cross compiling tool for clang build
        # apt-get install binutils-s390x-linux-gnu
        # clang-24 might not be officially released. Try a lower version if installation fails.
        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=$HOME/0day COMPILER=clang-24 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-24 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 prepare