make server: fix config setup for pkg build
make server: fix config setup for pkg build

When the server installs packages from source, it needs configuration
entry that points documentation indirections to the right place.
A relevant "config.rktd" is written, but to the wrong place, so
that it wasn't being used.

Merge to v6.0 (pending review)

mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket,mafagafogigante/racket