Separate out the JAVA_OPTIONS for the --dry-run

[lachlan-roberts]

Allow different JVM options to be set for the JVM which does the --dry-run than the one which runs the server.

Comment from @jnehlmeier in #160 (comment)_

If you go that route it would be great if the JAVA_OPTIONS used to run the server would be adjustable dynamically without rebuilding the image. Basically executing java $JAVA_OPTIONS -jar start.jar .... to start the server. This could be done by applying sed on the output of --dry-run to insert the $JAVA_OPTIONS variable. I mentioned something like that already in #151 (comment) because of JPMS.