@jpmeijers perhaps you would be interested in contributing to this?
You can see some examples:

• Add typescript support #64
• Dart support #49

I researched this for a while and got the build and resulting binary working fine, but I got stuck running it because our target container runs as root, and the way the Kotlin file is made executable using Spring Boot means it will always output a warning if it runs as root: streem/pbandk#73

@rvolosatovs are you familiar with gosu or su-exec? Do you think it makes sense to change our target image to use an unprivileged user to run protoc? We could probably create a user in an entrypoint and set it to the same permissions as the mounted workdir like this? We need to avoid making it a breaking change when doing this, for users that don't set a workdir...