multimedia/xvid: link with -znotext on i386

This port links some non-PIC code, which fails with lld as it defaults
to disallowing relocations against read-only segments. For i386 we can
just add -znotext unconditionally: for GNU BFD ld it just affirms BFD's
existing default.

PR: 214864, 230208
Approved by: bapt
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D17195