build: Pass BSDmakefile args to gmake

Minor convenience for platforms that doesn't have gmake installed
but prefer the habit of writing make instead of gmake.

test needs to live in .PHONY to get passed on to gmake.

PR-URL: https://github.com/iojs/io.js/pull/1298


Reviewed-By: Fedor Indutny <fedor@indutny.com>