reproduce (this is a W=1 build):
        # https://github.com/gourryinverse/linux/commit/928908d2d294d8615cea6bfcdf848b254485ebf6
        git remote add gourryinverse https://github.com/gourryinverse/linux
        git fetch --no-tags gourryinverse scratch/gourry/managed_nodes/rfc5
        git checkout 928908d2d294d8615cea6bfcdf848b254485ebf6

        # install s390 cross compiling tool for clang build
        # apt-get install binutils-s390x-linux-gnu
        # clang-23 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=$HOME/0day COMPILER=clang-23 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-23 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash mm/