How do I stop gcc on Darwin using the Next/Apple libobjc?

[Bill Northcott]

We are attempting to port a complex set of libraries (Swarm) originally 
written on NextStep to Darwin/MacOS X.  The source is mainly Objective-C 
with some C.

Unfortunately, although the language is ObjectiveC, Swarm uses a modified 
version of the gnu runtime which adds some extra functionality to the root 
object.

Currently we are having linking problems because gcc insists on linking 
against the Apple libobjc instead of our modified gnu version.

This would seem to be similar to problems encountered building GNUstep on 
Darwin, which is why I thought someone here might be able to help.  I have 
searched the archives without success.

Does anyone know how to get gcc on Darwin/MacOS X to link ObjectiveC with 
another runtime?

Bill Northcott

PS this will be cross posted to darwin-development.  My apologies if you 
receive both.