added empty out (#4757)

Summary:

~

Differential Revision: D61407442

Author: zonglinpeng

backends/cadence/aot/functions.yaml

@@ -57,6 +57,11 @@
     - arg_meta: null
       kernel_name: torch::executor::embedding_out
 
+- op: empty.out
+  kernels:
+    - arg_meta: null
+      kernel_name: torch::executor::empty_out
+
 - op: expand_copy.out
   kernels:
     - arg_meta: null

backends/cadence/reference/operators/CMakeLists.txt

@@ -49,7 +49,8 @@ set(_aten_ops__srcs
     "${EXECUTORCH_ROOT}/kernels/portable/cpu/op_to_copy.cpp"
     "${EXECUTORCH_ROOT}/kernels/portable/cpu/op_where.cpp"
     "${EXECUTORCH_ROOT}/kernels/portable/cpu/op_expand_copy.cpp"
-    "${EXECUTORCH_ROOT}/kernels/portable/cpu/op_gelu.cpp")
+    "${EXECUTORCH_ROOT}/kernels/portable/cpu/op_gelu.cpp"
+    "${EXECUTORCH_ROOT}/kernels/portable/cpu/op_empty.cpp")
 add_library(aten_ops_cadence ${_aten_ops__srcs})
 target_link_libraries(aten_ops_cadence PUBLIC executorch)
 target_link_libraries(aten_ops_cadence PRIVATE cadence_kernels)