Are there any good languages (with compilers) that let's you specify the data within a proto rather than the proto itself? I want to create files with configuration data in them, but they need to be compiled into proto format. I know Google has GCL, but as far as I can tell that isn't available in open source form, so I'm looking for an alternative. Ideally I'd like to be able to write a file that has the configuration data, then have it automatically compiled into a binary proto file as a part of my build process.