reproduce (this is a W=1 build):
        # https://github.com/avpatel/linux/commit/922a4bdf735544d2054881e7a06eefbeaf243aac
        git remote add avpatel https://github.com/avpatel/linux.git
        git fetch --no-tags avpatel riscv_sbi_dbtr_v2
        git checkout 922a4bdf735544d2054881e7a06eefbeaf243aac

        # install riscv cross compiling tool for clang build
        # apt-get install binutils-riscv64-linux-gnu
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # apt-get install llvm-dev

        # save the config file
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 ARCH=riscv olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 ARCH=riscv 
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 headers_install
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 -C tools/testing/selftests