Extracted from ab/9269995, target barbet-userdebug as follows:

/google/data/ro/projects/android/fetch_artifact --bid 9269995 --target barbet-userdebug 'barbet-img-9269995.zip'
unzip barbet-img-9269995.zip vendor.img
e2cp vendor.img:lib64/libprotobuf-cpp-full-3.9.1.so $ANDROID_BUILD_TOP/prebuilts/misc/android-arm64/protobuf/