cleanNative tasks do not remove jheader folder
For example:
$ gradle cleanNativeGlass
does not remove: "modules/graphics/build/generated-src/headers/"

One line fix:
felipe-mac:rt felipe$ hg diff
diff -r c8b31cd72210 build.gradle
--- a/build.gradle Fri Dec 13 10:01:50 2013 -0800
+++ b/build.gradle Fri Dec 13 10:20:43 2013 -0800
@@ -793,6 +793,7 @@
             }
             output = headerDir
             include(properties.javahInclude)
+ cleanTask.delete headerDir
         }
 
         def variants = properties.containsKey("variants") ? properties.variants : [""];