Download protoc automatically in the compile phase

[sekikn]

I tried to build the simple-protobuf example, but came across the following error:

$ ./mvnw clean install -f simple-protobuf/pom.xml

...

[ERROR] Failed to execute goal org.xolstice.maven.plugins:protobuf-maven-plugin:0.6.1:compile (default) on project apicurio-registry-examples-simple-protobuf: An error occurred while invoking protoc: Error while executing process.: Cannot run program "protoc": error=2, No such file or directory -> [Help 1]

Specifying the protocArtifact configuration seems to resolve it, just like the protobuf-validation module.