reproduce (this is a W=1 build):
        mkdir -p ~/bin
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install riscv cross compiling tool for clang build
        # apt-get install binutils-riscv-linux-gnu
        # https://github.com/c-sky/csky-linux/commit/1ff8b01f77a24e9bf21d6189f8913393494a2bd8
        git remote add csky-linux https://github.com/c-sky/csky-linux
        git fetch --no-tags csky-linux sg2042-master-qspinlock-64ilp32_v4
        git checkout 1ff8b01f77a24e9bf21d6189f8913393494a2bd8
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=riscv olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash drivers/gpu/drm/