reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/rdma/rdma.git/commit/?id=df1d75774b1284f7da22ed7db27204f70bb76ba2
        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 df1d75774b1284f7da22ed7db27204f70bb76ba2

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash drivers/infiniband/hw/irdma/