devel/lua-lgi: disable 5.4 build for now

Upstream releases do not currently build with Lua 5.4 due to lua_resume api
changes, and upsteam master doesn't currently work properly with Lua 5.4.

While here, appease stage-qa and fix the LIB_DEPENDS -- this port does
directly depend on libffi. Also pet portclippy (reorganization).

PORTREVISION bumped due to the dependency change.

PR: 250460
Submitted by: Andrew Gierth <andrew tao11 riddles org uk> (maintainer)