Proper way to extend device type/versions? Different codegen but same runtime

[adb]

@comaniac

Step 4 is the most important one. I feel like you can dispatch to a proper implementation in the codegen so that you don’t have to change Build?

This was my initial thought. I tried to check current target in the CodeGen stage so I could make the switch like I’m doing in the TOPI layer, but was getting a nullptr for the current target.