[superbuilder] toBuilder + singular + javac6 was broken

superbuilder generated the node `x.pluralName(plural == null ? Collections.emptyList() : plural)`.
java6 is not smart enough to infer the appropriate generics for the emptyList() call.
Fixed by always specifying the needed type explicitly: Collections.<String>emptyList();

test/transform/resource/after-delombok/SuperBuilderWithGenericsAndToBuilder.java

@@ -19,7 +19,7 @@ public class SuperBuilderWithGenericsAndToBuilder {
 			@java.lang.SuppressWarnings("all")
 			private static <A> void $fillValuesFromInstanceIntoBuilder(final SuperBuilderWithGenericsAndToBuilder.Parent<A> instance, final SuperBuilderWithGenericsAndToBuilder.Parent.ParentBuilder<A, ?, ?> b) {
 				b.field1(instance.field1);
-				b.items(instance.items == null ? java.util.Collections.emptyMap() : instance.items);
+				b.items(instance.items == null ? java.util.Collections.<Integer, String>emptyMap() : instance.items);
 			}
 			@java.lang.SuppressWarnings("all")
 			protected abstract B self();