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/brauner/linux/commit/ccb189ccdd283cf522b5112f7e5eab2817f48546
        git remote add brauner-github https://github.com/brauner/linux.git
        git fetch --no-tags brauner-github vfs-6.14.pidfs
        git checkout ccb189ccdd283cf522b5112f7e5eab2817f48546
        # 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 fs/