Cache moeNatJGen gradle task

I’ve got the moeNatJGen task coupled to one of my gradle source code compile tasks (using dependsOn), with the natjgen output pointing to somewhere in the build dir, because I do not want to trigger the natjgen manually all the time and don’t consider it part of my source code.

This works perfectly fine, however, it does make the app building time slower, which is ok if there is a change in the objc code. But if there’s no change, I would like gradle to cache the task using gradle’s input output comparison, and show, like all the other tasks, UP-TO-DATE in the logs whenever it was cached.
I was thinking something like this:

moeNatJGen {
	def nbcFile = file('objc.nbc')
	def nbc = new groovy.json.JsonSlurper().parseText(nbcFile.text)

	def nbcInput = nbc.bindings[0].headerPath + '/MyObjCHeader.h'
	def nbcOutput = nbc.output


But it doesn’t seem to have an impact, I’m never seeing moeNatJGen UP-TO-DATE.
Also tried:

outputs.upToDateWhen { 
      // This however never gets called

May have something to do with the code in moe gradle plugin NatJGen constructor, where upToDateWhen is always false:

Any tips to get this working properly?