from /usr/ports/distfiles when it wants to unpack modules during the
build, instead copy the files into the WRKDIR and point it there.
If there was a mistake with setting up MODGO_MODULES/MODGO_MODFILES
in a port then this change will cause it to show up in build, otherwise
it may succeed or fail randomly depending on what files are present in
distfiles (fetched by other ports).