reproduce:
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # apt-get install sparse
        # sparse version: v0.6.4-66-g0196afe1
        # https://github.com/avpatel/linux/commit/233eca2161c7836cf92bf250a33d68b01f98c01e
        git remote add avpatel https://github.com/avpatel/linux.git
        git fetch --no-tags avpatel riscv_acpi_b2_v6_610_rc1_full
        git checkout 233eca2161c7836cf92bf250a33d68b01f98c01e
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        ~/lkp-tests/kbuild/make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=riscv olddefconfig
        ~/lkp-tests/kbuild/make.cross C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=riscv SHELL=/bin/bash drivers/acpi/riscv/ drivers/iommu/riscv/