Fix builds w/ component=="shared_library" and v8_use_external_startup_data==1.

test/cctest/cctest.gyp

 # Copyright 2012 the V8 project authors. All rights reserved.
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
@@ skipping 241 matching lines @@
             'VCCLCompilerTool': {
               # MSVS wants this for gay-{precision,shortest}.cc.
               'AdditionalOptions': ['/bigobj'],
             },
           },
         }],
         ['component=="shared_library"', {
           # cctest can't be built against a shared library, so we need to
           # depend on the underlying static target in that case.
           'conditions': [
-            ['v8_use_snapshot=="true"', {
+            ['v8_use_snapshot=="true" and v8_use_external_startup_data==0', {
               'dependencies': ['../../tools/gyp/v8.gyp:v8_snapshot'],
-            },
-            {
-              'dependencies': [
-                '../../tools/gyp/v8.gyp:v8_nosnapshot',
-              ],
+            }],
+            ['v8_use_snapshot=="true" and v8_use_external_startup_data==1', {
+              'dependencies': ['../../tools/gyp/v8.gyp:v8_external_snapshot'],
+            }],
+            ['v8_use_snapshot!="true"', {
+              'dependencies': ['../../tools/gyp/v8.gyp:v8_nosnapshot'],
             }],
           ],
         }, {
           'dependencies': ['../../tools/gyp/v8.gyp:v8'],
         }],
       ],
     },
     {
       'target_name': 'resources',
       'type': 'none',
@@ skipping 24 matching lines @@
             '../../tools/js2c.py',
             '<@(_outputs)',
             'TEST',  # type
             '<@(file_list)',
           ],
         }
       ],
     },
   ],
 }