mail/fetchmail: Update 6.6.1 => 6.6.3

While here:

• Use <bsd.port.options.mk> instead.
• Add USES=localbase:ldflags instead.

Changelog:

• Fix compilation without SSL.
• Can now be built with OpenSSL 4.0.0.

https://gitlab.com/fetchmail/fetchmail/-/blob/6.6.3/NEWS?ref_type=tags

PR: 294251
Reported by: Corey Halpin <chalpin@cs.wisc.edu> (maintainer)
Approved by: vvd (co-mentor)