handle device=mps when loading DSOs by issuing warning and loading cpu model (#731)

Author: mikekgfb

build/builder.py

@@ -381,6 +381,10 @@ def _initialize_model(
         print(f"Time to load model: {time.time() - t0:.02f} seconds")
 
         try:
+            if "mps" in builder_args.device:
+                print("Warning: MPS currently does not support DSO models. Trying to load for CPU.")
+                builder_args.device = "cpu"
+                
             # Replace model forward with the AOT-compiled forward
             # This is a hacky way to quickly demo AOTI's capability.
             # model is still a Python object, and any mutation to its