Okay, there are two ways, one of which you can do, which is to trade from Dolphin Emulator to a GBA Emu, and once it is in the GBA, it is nothing since we know what to do from there. However, the emus are wonky, and you really gotta nurse in order to make it go through, but if you can do it, well, by all means.
Another way will have to involve homebrew, or a USB GCN Memory (like the one I had), that just transfers the save file into a real GCN memory card. Simple click and drags, done and done.