Just a few thoughts from a guy who is hasn't built a lot of guns. Take it with a grain of salt.
IF that crack is as deep as P.W. thinks, and the picture seems to show, you are probably still alright.
here's why:
Looks to me like it is still enormously fat on that side. Looking at the picture, the side with the crack (I'll assume it's a right handed gun, and the crack side is the side-plate side) looks to be twice the width of the lock side. Which means you can probably take half that wood off, right? If PW is right, the crack runs to about half the depth of the wood, and therefore would be completely, or almost completely gone when you shape the stock. Especially considering that you will take away the wood from the edge of the tang to the edge of the sideplate panel. I guess that 90% or more of that crack is in wood that will never be on the gun. (hard to say about further down the wrist though...)
If you do decide to super glue it, use the Thin Zap-a-Gap CA stuff. Don't buy the cheapo box store stuff. Zap-a-Gap is excellent ( I also used to make RC airplanes, and that stuff is really good). I would not use the accelerator. Just let it soak in and dry on its own. Realize that if you put the thin CA in now, before removing more wood, the CA may not go all the way in to the deepest end of the crack. It dries quickly, so may form a dam, preventing it from going the whole way.
So, you might stabilize the crack now, so you don't have chip-outs as you rasp the gun to shape. Then remove wood after you have the tang in and the side panel drawn. As you remove wood, you might find that you get to a point where the CA has not penetrated and need to glue it again.
I hope that all makes sense.
Last thing:
The second time you open the CA bottle, the top might be stuck to the bottle from leaked CA. Do not, I say again, Do Not grip the cap in your teeth and pull the bottle away from your face. Super fast drying, super strong CA might just splash out of the bottle and stick your eyelids to your face.
Ask me how I know.
Cheers,
Norm