The new build infrastructure wants to fully automate the generation of the JNI header files (running javah).
On classes that have "native" methods this is obvious, but class that only export constants, and whose constants are needed in the JNI native code, we need to mark these classes as needing their native header file generated.

This change proposes adding:

import javax.tools.annotation.GenerateNativeHeader;
  
/* No native methods here, but the constants are needed in the supporting JNI code */
@GenerateNativeHeader


To any class without a native method, but needing to expose it's constants to the native code.