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://github.com/gestionlin/linux/commit/7315604eb1d087836123bc9670d2be420a42d37f
        git remote add linyunsheng https://github.com/gestionlin/linux.git
        git fetch --no-tags linyunsheng page_frag_cache_prototype
        git checkout 7315604eb1d087836123bc9670d2be420a42d37f
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-19 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-19 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash net/mptcp/