Binary JDK packages

[Robert Swindells <rjs%fdy2.co.uk@localhost>]

I have pushed two incomplete packages to wip for JDK 17 and 21 LTS
builds from the Adoptium project - temurin17 & temurin21.

They build for Linux x86_64, not updated the PLISTs for other platforms.

Could use some help in working out how to handle the different
architectures in the Makefile.

I think they should replace the lang/oracle-jdk?? ones soon to avoid
users getting caught out by the Oracle licencing terms.