Extract create_sdk build rule to own file to avoid cycle.

dart/create_sdk.gyp

+# Copyright (c) 2014, 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.
+
+{
+  'targets': [
+    {
+      'target_name': 'create_sdk',
+      'type': 'none',
+      'dependencies': [
+        'runtime/dart-runtime.gyp:dart',
+        'utils/compiler/compiler.gyp:dart2js',
+        'utils/pub/pub.gyp:pub',
+        'utils/dartfmt/dartfmt.gyp:dartfmt',
+        'editor/analyzer.gyp:analyzer',
+      ],
+      'actions': [
+        {
+          'action_name': 'create_sdk_py',
+          'inputs': [
+            '<!@(["python", "tools/list_files.py", "\\.dart$", "sdk/lib"])',
+            '<!@(["python", "tools/list_files.py", "", '
+                '"sdk/lib/_internal/lib/preambles"])',
+            '<!@(["python", "tools/list_files.py", "", "sdk/bin"])',
+            'tools/create_sdk.py',
+            '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)dart<(EXECUTABLE_SUFFIX)',
+            '<(SHARED_INTERMEDIATE_DIR)/dart2js.dart.snapshot',
+            '<(SHARED_INTERMEDIATE_DIR)/utils_wrapper.dart.snapshot',
+            '<(SHARED_INTERMEDIATE_DIR)/pub.dart.snapshot',
+            '<(PRODUCT_DIR)/dartanalyzer/dartanalyzer.jar',
+            '<(SHARED_INTERMEDIATE_DIR)/dartfmt.dart.snapshot',
+            'tools/VERSION'
+          ],
+          'outputs': [
+            '<(PRODUCT_DIR)/dart-sdk/README',
+          ],
+          'action': [
+            'python',
+            'tools/create_sdk.py',
+            '--sdk_output_dir', '<(PRODUCT_DIR)/dart-sdk',
+            '--snapshot_location', '<(SHARED_INTERMEDIATE_DIR)/'
+          ],
+          'message': 'Creating SDK.',
+        },
+      ],
+    },
+  ],
+}