Skip subdir test with ddc

Seems like we can't load multiple ddc entrypoints

_test/dart_test.yaml

@@ -4,10 +4,14 @@ timeout: 16x
 concurrency: 1
 
 tags:
-  integration:
   # This tag is used for integration tests - we don't need special options at the
   # moment, but want to avoid warnings from the test runner about using undefined
   # targets.
+  integration:
+  # Used for subdir_source_test.dart, which deliberately includes multiple Dart
+  # entrypoints where one is from a subdirectory. Multiple entrypoints don't
+  # appear to work with ddc, so we skip this test when running ddc tests.
+  multiple-entrypoints:
 
 define_platforms:
   chrome_without_wasm:

_test/mono_pkg.yaml

@@ -10,8 +10,8 @@ stages:
   - analyze: --fatal-infos .
     os: linux
 - unit_test:
-  - command: dart run build_runner test -- -p chrome --test-randomize-ordering-seed=random
-  # TODO(https://github.com/dart-lang/build/issues/3423): restore this on windows 
+  - command: dart run build_runner test -- -p chrome --test-randomize-ordering-seed=random -x multiple-entrypoints
+  # TODO(https://github.com/dart-lang/build/issues/3423): restore this on windows
   - command: dart run build_runner test -- -p vm test/configurable_uri_test.dart --test-randomize-ordering-seed=random
     os: linux
 - e2e_test:

_test/test/subdir_source_test.dart

@@ -1,6 +1,9 @@
 // Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
+@Tags(['multiple-entrypoints'])
+library;
+
 import 'dart:js_interop';
 import 'dart:js_interop_unsafe';