openjdk20-zulu: install files under ${prefix}

[breun]

Description

Install all actual files under ${prefix}, only create a symlink under /Library/Java/JavaVirtualMachines, as suggested on https://trac.macports.org/ticket/67935.

Type(s)

• enhancement

Tested on

macOS 13.5 22G74 arm64
Xcode 14.3.1 14E300c

Verification

Have you

• followed our Commit Message Guidelines?
• squashed and minimized your commits?
• checked that there aren't other open pull requests for the same change?
• referenced existing tickets on Trac with full URL?
• checked your Portfile with port lint --nitpick?
• tried existing tests with sudo port test?
• tried a full install with sudo port -vst install?
• tested basic functionality of all binary files?
• checked that the Portfile's most important variants haven't been broken?