Fix for JDK-8144857 wasn't enough. Depending on $(BUILD_DEMO_JAVA_POLLER_COMPILE_TARGETS) doesn't guarantee that the header file is there in all cases. There is a separate copy step of headers inside SetupJavaCompilation. The simple solution to this is to just depend on $(BUILD_DEMO_JAVA_Poller) instead. Not ideal for efficiency, but in this small case it hardly matters.