Dtype selective build: disable when not in xplat and add fail msg

Differential Revision: D75256223

Pull Request resolved: #11090

Author: lucylq

examples/selective_build/targets.bzl

@@ -65,7 +65,7 @@ def define_common_targets():
         deps = [
             ":select_ops_in_dict",
         ],
-        dtype_selective_build = True,
+        dtype_selective_build = is_xplat(),
         visibility = ["//executorch/..."],
     )
 
@@ -78,7 +78,7 @@ def define_common_targets():
         deps = [
             ":select_ops_in_dict",
         ],
-        dtype_selective_build = True,
+        dtype_selective_build = is_xplat(),
         visibility = ["//executorch/..."],
     )
 

shim_et/xplat/executorch/codegen/codegen.bzl

@@ -644,8 +644,7 @@ def executorch_generated_lib(
 
     if dtype_selective_build:
         if not expose_operator_symbols and not is_xplat():
-            # TODO(T225169282): make this a fail once internal cases move to xplat.
-            warning("""
+            fail("""
                 Dtype selective build with expose_operator_symbols=False works only in xplat -
                 there are undefined symbols otherwise. Please try to use xplat, or talk to the
                 executorch team. Setting expose_operator_symbols=True is not recommended as the