Fix BUILD.gn to load the correct V8 snapshot configuration

samples/BUILD.gn

 # Copyright 2014 PDFium 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/config/sanitizers/sanitizers.gni")
+import("//build_overrides/v8.gni")
 import("../pdfium.gni")
 
 group("samples") {
   testonly = true
   deps = [
     ":pdfium_test",
     ":pdfium_diff",
   ]
 }
 
@@ skipping 31 matching lines @@
   ]
   if (!pdf_enable_xfa) {
     deps += [ "../third_party:fx_lpng" ]
   }
   if (pdf_enable_v8) {
     deps += [ "//v8:v8_libplatform" ]
     include_dirs = [
       "//v8",
       "//v8/include",
     ]
+    configs += [ "//v8:external_startup_data" ]
   }
   configs += [ ":pdfium_samples_config" ]
 }
 
 executable("pdfium_diff") {
   testonly = true
   sources = [
     "image_diff.cc",
     "image_diff_png.cc",
     "image_diff_png.h",
   ]
   deps = [
     "//build/config/sanitizers:deps",
     "//third_party/pdfium",
   ]
   if (!pdf_enable_xfa) {
     deps += [ "../third_party:fx_lpng" ]
   }
   configs -= [ "//build/config/compiler:chromium_code" ]
   configs += [
     ":pdfium_samples_config",
     "//build/config/compiler:no_chromium_code",
   ]
 }