Hi,
Recently after devel/mongo-c-driver update, nginx ports had been modified but later joneum@ came with a better idea that is to use pkgconfig instead.
I have made the patch but kept joneum@ as the author since the code is from them.
I have tested build in Poudriere with GRIDFS option enabled on 14.4-RELEASE-amd64-main-26a43cbfefb4 and it seems OK.
Thanks.