thunderbird port - a few issues

[Eitan Adler]

WANT_GNOME= yes
should that be WANT_GNOME or WITH_GNOME?

We should add --disable-tests to MOZ_OPTIONS unless WITH_DEBUG is enabled.

Lastly:
$portlint
WARN: Makefile: [45]: use of != in assignments is almost never a good
thing to do.  Try to avoid using them.  See
http://lists.freebsd.org/pipermail/freebsd-ports/2008-July/049777.html
for some helpful hints on what to do instead.
could

GECKO_PTHREAD_LIBS!=${CC} -dumpspecs | ${GREP} pthread | ${SED} -e
's|^.*%{\!pg: %{pthread:|| ; s|}.*$$||' || ${TRUE}

be rewritten ?