reproduce (this is a W=1 build):
        # https://github.com/brauner/linux/commit/16905bac11a0bd08362a07a222b1650db0bff1ec
        git remote add brauner-github https://github.com/brauner/linux.git
        git fetch --no-tags brauner-github work.procfs.cleanup
        git checkout 16905bac11a0bd08362a07a222b1650db0bff1ec

        # 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=$HOME/0day COMPILER=clang-17 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-17 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash net/l2tp/