javac source & target

Hi,

I'm looking into the PR "Mk/bsd.default-versions.mk: update JAVA_DEFAULT to 21".
  https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=272855

Quiet some work involves changing hardcoded -source -target settings to javac. Quite some ports have targets lower than 8 which is not supported by recent javac version.

/usr/local/openjdk21/bin/javac --help:
  --target <release>, -target <release>
        Generate class files suitable for the specified Java SE release.
        Supported releases: 
            8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21

Openjdk17 supports 7-17 and openjdk25 supports 8-25. Mind that java can read classes going back to version 1. It is just that the javac compiler can't generate them anymore.

To make class files usable between ports I think it is user friendly to compile targeted for the oldest JDK in the ports tree which is now openjdk8.
Or we can aim to remove the source/target definitions and compile for JAVA_DEFAULT.
Unfortunately these source/target definitions are often hardcoded in the source code of the port so we need to patch anyways.

What are your thoughts on this?

Regards,
Ronald.