reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git/commit/?id=23669ca628b3c39dc3cc43a5b4b93b4b5ab4d58c
        git remote add rdma-rdma https://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git
        git fetch --no-tags rdma-rdma wip/leon-for-next
        git checkout 23669ca628b3c39dc3cc43a5b4b93b4b5ab4d58c

        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=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash