I think you should be ok building on the fast machine with the different CPU... if you run into trouble, it'll be pretty easy to add things to CFLAGS to specify a generic CPU type. The build system is smart enough to only rebuild what's needed, usually no need to do 'make clean'. If your fast box has many cores, you might want to do "make depend && make -j8" rather than just "make -j8", as sometimes make depend explodes when there are many cores. If you touch the build system itself, you might have to regenerate it, but you only need to do that when doing things like adding new dlls.
