[arch-general] Package guidelines for apps requiring a specific Java version

[Maxwell Anselm]

> What is the name/URL of this app?
It's the GURPS character sheet: http://gurpscharactersheet.com/
I have a github repo for my WIP AUR package:
https://github.com/silverhammermba/gcs

> If building on a box where multiple JVM can be installed: build
> scripts for Java apps usually provide a "--with-jdk=<PATH>" or
> "--java-home=<PATH>" (or similar) to force the JVM to use to build. If
> true for the app you are trying to build then you could use path
> "/usr/lib/jvm/java-8-openjdk/"
Yeah, my primary concern here is multi-JVM boxes. If only Java 8 is
installed, there's no issue. The build system is Apache Ant, and I can
change the JVM it uses by setting JAVA_HOME for makepkg, but even then I
can't assume that Java 8 is java-8-openjdk. For example jre from the AUR
also provides java-runtime=8.

I feel like the archlinux-java script should be able to get/set the default
Java **per version**. That would make it much easier to handle all this.