reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/leon/linux-rdma.git/commit/?id=cd9d1bc985fe78bf150400d89184d41054810e8e
        git remote add leon-rdma https://git.kernel.org/pub/scm/linux/kernel/git/leon/linux-rdma.git
        git fetch --no-tags leon-rdma dmabuf-vfio
        git checkout cd9d1bc985fe78bf150400d89184d41054810e8e
        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=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=sparc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=sparc SHELL=/bin/bash arch/sparc/mm/