reproduce (this is a W=1 build):
        git remote add android-common https://android.googlesource.com/kernel/common
        git fetch --no-tags android-common android-mainline
        git checkout 9d47057e55785b27694b8e0967f7fe8720bc41b3
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash drivers/dma-buf/