Use auto-generated v8 version when building.

BUILD.gn

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Because standalone V8 builds are not supported, assume this is part of a
 # Chromium build.
 import("//build/module_args/v8.gni")
 
 # TODO(jochen): These will need to be user-settable to support standalone V8
 # builds.
@@ skipping 962 matching lines @@
     "src/utils-inl.h",
     "src/utils.cc",
     "src/utils.h",
     "src/v8.cc",
     "src/v8.h",
     "src/v8memory.h",
     "src/v8threads.cc",
     "src/v8threads.h",
     "src/variables.cc",
     "src/variables.h",
-    "src/version.cc",
+    "src/version_gen.cc",
     "src/version.h",
     "src/vm-state-inl.h",
     "src/vm-state.h",
     "src/zone-inl.h",
     "src/zone.cc",
     "src/zone.h",
     "src/third_party/fdlibm/fdlibm.cc",
     "src/third_party/fdlibm/fdlibm.h",
   ]
 
@@ skipping 561 matching lines @@
       sources += [
         "src/d8-debug.cc",
         "$target_gen_dir/d8-js.cc",
       ]
     }
     if (v8_enable_i18n_support) {
       deps += [ "//third_party/icu" ]
     }
   }
 }