reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/hare/scsi-devel.git/commit/?id=95eeb6714114cd17d9c4c494a28cc11d86059eef
        git remote add hare-scsi-devel https://git.kernel.org/pub/scm/linux/kernel/git/hare/scsi-devel.git
        git fetch --no-tags hare-scsi-devel configfs-ns.v6
        git checkout 95eeb6714114cd17d9c4c494a28cc11d86059eef

        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # apt-get install sparse
        # sparse: v0.6.5-rc1

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=riscv olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=riscv SHELL=/bin/bash drivers/nvme/target/