Hotfix package builder emitting JSON with missing keys for empty values

The meaning of `mapper.setSerializationInclusion` changed with the
Jackson upgrade, which meant that empty collections were being fully
stripped from the output. Fix by changing the strategy to NON_ABSENT,
which only strips nulls and "absent" values like Optional.absent

launcher-builder/src/main/java/com/skcraft/launcher/builder/PackageBuilder.java

@@ -407,7 +407,7 @@ public static void main(String[] args) throws IOException, InterruptedException
         // Initialize
         SimpleLogFormatter.configureGlobalLogger();
         ObjectMapper mapper = new ObjectMapper();
-        mapper.setSerializationInclusion(JsonInclude.Include.NON_DEFAULT);
+        mapper.setSerializationInclusion(JsonInclude.Include.NON_ABSENT);
 
         Manifest manifest = new Manifest();
         manifest.setMinimumVersion(Manifest.MIN_PROTOCOL_VERSION);