reproduce (this is a W=1 build):
        git remote add nf-next https://git.kernel.org/pub/scm/linux/kernel/git/netfilter/nf-next.git
        git fetch nf-next main
        git checkout nf-next/main
        b4 shazam https://lore.kernel.org/r/20260525201116.407338-2-kacper.kokot.44@gmail.com

        # install s390 cross compiling tool for clang build
        # apt-get install binutils-s390x-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=$HOME/0day COMPILER=clang-18 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-18 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash net/netfilter/