gcc34 -- To thunk or not to thunk?

[walt]

Since the mozilla-devel port won't compile with gcc2 lately I've
been trying to use gcc34.  The problem is that the code wants to
know whether the compiler 'thunks', and uses the ostype/platform
name to decide the question so it can set these variables:

#define CFRONT_STYLE_THIS_ADJUST
#else
#define THUNK_BASED_THIS_ADJUST
#endif

Well, mozilla doesn't know about DFly yet, so I need to know
how to set the variable above.  I've tried both settings and
mozilla compiles okay but segfaults either way :o/

Any ideas?