jextract used to generate enum constants in the header file as private final constants in the main interface.

With JDK-8201935, those constants are generated as instance methods. JDK-8212560 enables to create a static forwarder class which will generate static constants.

However, such static forwarder class is only generated when -l is specified with jextract.

To provide a consistent user experience, we can 1) make -l a required argument, which is desired since beginning anyway as we also want to verify function symbols exist. or 2) Provide other means to get enum constants.