[Executorch][llama] Hookup use_attention_mask option in the source transforms inside llm mananger

examples/models/llama/export_llama_lib.py

@@ -1227,10 +1227,22 @@ def _get_source_transforms(  # noqa
     if args.expand_rope_table:
         transforms.append(materialze_broadcast_of_rope_freq_cis)
 
+    use_attention_mask_for_custom_sdpa = False
+    if isinstance(args, argparse.Namespace):
+        if getattr(args, "use_custom_sdpa_with_attention_mask", None):
+            use_attention_mask_for_custom_sdpa = True
+
     if args.use_sdpa_with_kv_cache:
         transforms.append(replace_kv_cache_with_custom_kv_cache)
         # todo: do this optionally
-        transforms.append(replace_sdpa_with_custom_op)
+        # if use attention mask instead of causal attention
+        # then create partial function that sets use_attention_mask=True
+        if use_attention_mask_for_custom_sdpa:
+            transforms.append(
+                partial(replace_sdpa_with_custom_op, use_attention_mask=True)
+            )
+        else:
+            transforms.append(replace_sdpa_with_custom_op)
 
     if args.quantize_kv_cache:
         assert args.use_kv_cache, "quantize_kv_cache requires use_kv_cache=True"