reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # install s390 cross compiling tool for clang build
        # apt-get install binutils-s390x-linux-gnu
        # https://git.kernel.org/pub/scm/linux/kernel/git/djiang/linux.git/commit/?id=6cf5361c36766f6ea8fc0ff6bc80407cd343168e
        git remote add djiang https://git.kernel.org/pub/scm/linux/kernel/git/djiang/linux.git
        git fetch --no-tags djiang cxl/fwctl
        git checkout 6cf5361c36766f6ea8fc0ff6bc80407cd343168e
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash drivers/cxl/core/