Build core library stubs as part of building the SDK.

utils/pub/pub.gyp

Index: utils/pub/pub.gyp
diff --git a/utils/pub/pub.gyp b/utils/pub/pub.gyp
index e16d910e46db6f67409848ec0313c87d5e8b29d6..bb1d429c521ac1268ce5bc80cc48c05ecb33ac43 100644
--- a/utils/pub/pub.gyp
+++ b/utils/pub/pub.gyp
@@ -36,6 +36,34 @@
         },
       ],
     },
+    {
+      'target_name': 'core_stubs',
+      'type': 'none',
+      'dependencies': [
+        '../../runtime/dart-runtime.gyp:dart',
+        '../../pkg/pkg.gyp:pkg_packages',
+        '../../pkg/pkg_files.gyp:pkg_files_stamp'
+      ],
+      'actions': [
+        {
+          'action_name': 'generate_core_stubs',
+          'inputs': [
+            '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)dart<(EXECUTABLE_SUFFIX)',
+            '../../sdk/lib/_internal/libraries.dart',
+            '<(SHARED_INTERMEDIATE_DIR)/pkg_files.stamp',
+          ],
+          'outputs': [
+            '<(SHARED_INTERMEDIATE_DIR)/core_stubs/dart_io.dart',
+          ],
+          'action': [
+            '<(PRODUCT_DIR)/<(EXECUTABLE_PREFIX)dart<(EXECUTABLE_SUFFIX)',
+            '--package-root=<(PRODUCT_DIR)/packages/',
+            '../../pkg/stub_core_library/bin/stub_core_library.dart',
+            '<(SHARED_INTERMEDIATE_DIR)/core_stubs',
+          ],
+        }
+      ]
+    },
     # Other targets depend on pub files, but have to many inputs, which causes
     # issues on some platforms.
     # This target lists all the files in sdk/lib/_internal/pub,