Add buck2 build and run test model to pull.yml

Summary: Buck build the demo binary `size_test_all_ops` and export a test model `ModuleLinear.ff`, then run the model.

Differential Revision: D47737752

fbshipit-source-id: 7cfb5b74f4b96a8c9a61a6351a68c0ef18ecb313

Author: larryliu0820

.github/workflows/pull.yml

@@ -31,3 +31,12 @@ jobs:
 
         # Just print out the list of packages for debugging
         pip list
+
+        # Build executorch runtime
+        buck2 build //test:size_test_all_ops
+
+        # Export a test model
+        python3 test/models/export_program --modules=ModuleLinear --outdir=./
+
+        # Run test model
+        buck2 run //test:size_test_all_ops ./ModuleLinear.ff