Add -ldl linker flag to libdart_builtin link step.

runtime/bin/bin.gypi

 # Copyright (c) 2012, 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.
 
 {
   'variables': {
     'io_cc_file': '<(SHARED_INTERMEDIATE_DIR)/io_gen.cc',
     'json_cc_file': '<(SHARED_INTERMEDIATE_DIR)/json_gen.cc',
     'uri_cc_file': '<(SHARED_INTERMEDIATE_DIR)/uri_gen.cc',
     'utf8_cc_file': '<(SHARED_INTERMEDIATE_DIR)/utf8_gen.cc',
@@ skipping 201 matching lines @@
         'builtin_impl_sources.gypi',
         '../platform/platform_sources.gypi',
       ],
       'sources/': [
         ['exclude', '_test\\.(cc|h)$'],
       ],
       'conditions': [
         ['OS=="win"', {'sources/' : [
           ['exclude', 'fdutils.h'],
         ]}],
+        ['OS=="linux"',
+         {'ldflags': ['-ldl',],
+        }],
       ],
     },
     {
       'target_name': 'libdart_withcore',
       'type': 'static_library',
       'dependencies': [
         'libdart_lib_withcore',
         'libdart_vm',
         'libjscre',
         'libdouble_conversion',
@@ skipping 179 matching lines @@
           ],
           'include_dirs': [
             '.',
           ],
           'sources': [
             'test_extension_linux.cc',
           ],
           'defines': [
             'DART_SHARED_LIB',
           ],
-          'ldflags': [
-            '-ldl',
-          ],
         },
       ],
     }],
   ],
 }