static ConfigInstance buildInstance(ConfigInstance.Builder builder, InnerCNode targetDef) {
        try {
            if (targetDef != null) applyDef(builder, targetDef);
            Class<? extends ConfigInstance> clazz = getConfigClass(builder.getClass());
            return clazz.getConstructor(builder.getClass()).newInstance(builder);
        } catch (Exception e) {
            throw new ConfigurationRuntimeException(e);
        }
    }
Builds a ConfigInstance from a ConfigInstance.Builder.
(Put here not in ConfigInstance.Builder temporarily to work around dependency problems.)
configserver/src/main/java/com/yahoo/vespa/config/server/application/ConfigInstanceBuilder.java