Add buck2 build and run test model to pull.yml (#18)

Summary:
Pull Request resolved: #18

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

Reviewed By: huydhn, cccclai

Differential Revision: D47737752

fbshipit-source-id: d776ea09dd1e8d31a5b361f6e090b85e4de495e8

Author: larryliu0820

.github/workflows/pull.yml

@@ -40,3 +40,12 @@ 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 examples/export/export_example.py --model_name="linear"
+
+        # Run test model
+        buck2 run //test:size_test_all_ops ./linear.ff