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/mcgrof/linux.git/commit/?id=58ad1a2b2d0abfd272e05e695cd4c635f49e934e
        git remote add mcgrof https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux.git
        git fetch --no-tags mcgrof 20250423-v6.15-rc3-ext4-fix
        git checkout 58ad1a2b2d0abfd272e05e695cd4c635f49e934e
        # 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 mm/