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

test/unittests/unittests.gyp

 # Copyright 2014 the V8 project authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   'variables': {
     'v8_code': 1,
   },
   'includes': ['../../build/toolchain.gypi', '../../build/features.gypi'],
   'targets': [
@@ skipping 88 matching lines @@
         }],
         ['v8_target_arch=="x64"', {
           'sources': [  ### gcmole(arch:x64) ###
             'compiler/x64/instruction-selector-x64-unittest.cc',
           ],
         }],
         ['component=="shared_library"', {
           # compiler-unittests 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'],
         }],
         ['os_posix == 1', {
           # TODO(svenpanne): This is a temporary work-around to fix the warnings
           # that show up because we use -std=gnu++0x instead of -std=c++11.
           'cflags!': [
             '-pedantic',
           ],
           'direct_dependent_settings': {
             'cflags!': [
               '-pedantic',
             ],
           },
         }],
       ],
     },
   ],
 }