Add native extensions to the Dart shell, on the linux platform.

runtime/dart-runtime.gyp

 # Copyright (c) 2011, 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.
 
 {
   'includes': [
     'vm/vm.gypi',
     'bin/bin.gypi',
     'third_party/double-conversion/src/double-conversion.gypi',
     'third_party/jscre/jscre.gypi',
@@ skipping 17 matching lines @@
         'include/dart_debugger_api.h',
         'vm/dart_api_impl.cc',
         'vm/debugger_api_impl.cc',
       ],
       'direct_dependent_settings': {
         'include_dirs': [
           'include',
         ],
       },
     },
+    {
+      # The Dart API is exported from this library to dynamically loaded shared
+      # libraries.
+      'target_name': 'libdart_export',
+      'type': 'static_library',
+      'dependencies': [
+        'libdart_lib',
+        'libdart_vm',
+        'libjscre',
+        'libdouble_conversion',
+      ],
+      'include_dirs': [
+        '.',
+      ],
+      'sources': [
+        'include/dart_api.h',
+        'include/dart_debugger_api.h',
+        'vm/dart_api_impl.cc',
+        'vm/debugger_api_impl.cc',
+      ],
+      'defines': [
+        'DART_SHARED_LIB',
+      ],
+      'direct_dependent_settings': {
+        'include_dirs': [
+          'include',
+        ],
+      },
+    },
   ],
 }