Get `jlink` up and running

[sormuras]

java --module-path .bach\workspace\modules;.bach\external-modules --module com.github.sormuras.bach.helidon works.

jlink reports (for example): Error: automatic module cannot be used with jlink: io.opentracing.api from file:///D:/dev/github/sormuras/bach-helidon/.bach/external-modules/opentracing-api-0.33.0.jar

This goes for all automatic modules.