cad/ghdl: Update 5.1.1 => 6.0.0
- Add WWW for main site
- Fix SYNTH logic to optionally disable it as by default synth is enabled https://github.com/ghdl/ghdl/blob/e589c698c351369ac5bcfe7abe1f1152ac5d4727/configure#L52
- Simplify stripping logic in post-install phase
Approved by: yuri@ (maintainer, Mentor)
Approved by: db@, yuri@ (Mentors, implicit)
Differential Revision: https://reviews.freebsd.org/D56078