Log Message:
From Ken'ichi Fukamachi in PR 45992:
(1) specify PKG_OPTIONS.ng= -canna in /etc/mk.conf.

        ng's Makefile expects the environment variable of USE_CANNA
        always, but the current Makefile does not consider it.

(2) compile ng on system-V like platforms e.g. *-linux, Solaris.

        We need to edit ng's Makefile on platforms, but the current
        pkgsrc Makefile is only suitable for BSD platforms.