> > How do I do that?
> 
> I don't know, show me the CMakeLists.txt

I'm not sure, but perhaps this one?

rosegarden/src/CMakeLists.txt

> > Second, why is that needed for 64-bit and not 32-bit?
> 
> Not sure. Maybe you have another gcc version on 32 bit machine?

Should not be. Everything recently was updated.

Darrell