reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git/commit/?id=9f7fa197442610db1e5e9a38c3a1e21520593843
        git remote add ardb https://git.kernel.org/pub/scm/linux/kernel/git/ardb/linux.git
        git fetch --no-tags ardb lockless-random-v2
        git checkout 9f7fa197442610db1e5e9a38c3a1e21520593843

        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=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash drivers/char/