Review Request: JDK-8155955: packager needs to determine the root modules to create JRE image

[Mandy Chung]

http://cr.openjdk.java.net/~mchung/jdk9/webrevs/8155955/webrev.02

With further discussion with Chris Bensen and others, we agree that the packager would require the presence of the packaged module of jdk.packager to be present matching the runtime version of the image being created.  The packager will determine the root modules and invoke jlink to create the resulting image for a non-modular application.  To get the root modules for a release, one solution is to generate that list at build time.

ModuleFinder currently finds modules for runtime. packager will need to detect if the packaged module of jdk.packager is found and matching the version of the resulting image being created.  This patches provides an API to get a ModuleFinder configured for link phase and JDK-8147894 will refresh the jlink API to support that.

Mandy