GraalVM native image example incompatible with GraalVM 20.3.0 due to deprecated command-line options

[timmattison]

With GraalVM 20.3.0 I get this error when trying to build the native image example:

Error: Non-boolean option 'TraceClassInitialization' can not use +/- prefix. Use 'TraceClassInitialization=<value>' format

I would submit a PR for this but I'm not sure if that would break versions below 20.3.0. I'm also not sure what values I should add there since it's no longer a boolean option. I believe that it wants a list of classes instead.

[zachgk]

The flag is used for debugging. I think you can just remove it