Download protobuf-ruby-<version>.tar.gz from 
https://github.com/google/protobuf/releases

Extract and copy ruby directory to create google-protobuf-<version>

tar -zxvf protobuf-ruby-<version>.tar.gz
mv protobuf-ruby-<version>/ruby google-protobuf-<version>
tar -zcvf ruby-protobuf-ruby-<version>.tar.gz google-protobuf-<version>
