reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # install riscv cross compiling tool for clang build
        # apt-get install binutils-riscv64-linux-gnu
        # clang-21 might not be officially released. Try a lower version if installation fails.
        # https://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git/commit/?id=5071e94f47af4227e0029598a6c07a26cefb6bf5
        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 5071e94f47af4227e0029598a6c07a26cefb6bf5
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash drivers/infiniband/core/