Is there any way to use ARC in 32-bit?

[Jens Alfke]

I'm investigating getting a large iOS/Mac codebase to run on Linux via GNUstep. 
The latest roadblock I've run into is that if I enable ARC (clang flag 
-fobjc-arc) I get an error that "-fobjc-arg is not supported on platforms using 
the legacy runtime".

I'm building for 32-bit, because the eventual target platform is an embedded 
system that's almost certainly 32-bit. Is there any way to get this to work? 
Apple's Obj-C implementation supports a 'modern' runtime in 32-bit, although 
it's only used in iOS for reasons of backward compatibility. Does the GNUstep 
Obj-C runtime have similar support, and if so how would I enable it?

(Not using ARC is not an option … the amount of work to take it out would be 
prohibitive.)

—Jens