Fix BUILD.gn to load the correct V8 snapshot configuration

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.
 
+import("//build_overrides/v8.gni")
 import("//testing/test.gni")
 import("pdfium.gni")
 
 config("pdfium_config") {
   cflags = []
   include_dirs = [
     ".",
     "third_party/freetype/include",
     "third_party/freetype/include/freetype",
   ]
@@ skipping 148 matching lines @@
   include_dirs = []
   if (pdf_enable_v8) {
     deps += [
       "//v8",
       "//v8:v8_libplatform",
     ]
     include_dirs += [
       "//v8",
       "//v8/include",
     ]
+    configs += [ "//v8:external_startup_data" ]
   }
   configs += [ ":pdfium_config" ]
 }
 
 # Targets below this are only visible within this file (and to the
 # top-level gn_visibility target used to help gn_all build everything).
 visibility = [
   ":*",
   "//:gn_visibility",
 ]
@@ skipping 498 matching lines @@
       "fpdfsdk/src/javascript/util.h",
       "fpdfsdk/src/jsapi/fxjs_v8.cpp",
     ]
     include_dirs = [
       "//v8",
       "//v8/include",
     ]
     public_deps = [
       "//v8",
     ]
+    configs += [ "//v8:external_startup_data" ]
   } else {
     sources += [ "fpdfsdk/src/javascript/JS_Runtime_Stub.cpp" ]
   }
   configs += [ ":pdfium_config" ]
 }
 
 static_library("formfiller") {
   sources = [
     "fpdfsdk/include/formfiller/FFL_CBA_Fontmap.h",
     "fpdfsdk/include/formfiller/FFL_CheckBox.h",
@@ skipping 72 matching lines @@
   if (pdf_enable_v8) {
     sources += [ "fpdfsdk/src/jsapi/fxjs_v8_embeddertest.cpp" ]
     deps += [
       "//v8",
       "//v8:v8_libplatform",
     ]
     include_dirs += [
       "//v8",
       "//v8/include",
     ]
+    configs += [ "//v8:external_startup_data" ]
   }
   configs += [ ":pdfium_config" ]
 }