reproduce:
        # apt-get install sparse
        # sparse version: v0.6.4-52-g1cf3d98c-dirty
        # https://github.com/davidhildenbrand/linux/commit/e65050eda564d19ea9e6dc8dd3d5e5ccc69bc6ec
        git remote add davidhildenbrand https://github.com/davidhildenbrand/linux
        git fetch --no-tags davidhildenbrand rmap_batching
        git checkout e65050eda564d19ea9e6dc8dd3d5e5ccc69bc6ec
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 olddefconfig
        make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=x86_64 SHELL=/bin/bash mm/