Move v8_use_external_startup_data out of //build/config:feature_flags.

gin/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")
 
 component("gin") {
   sources = [
     "arguments.cc",
@@ skipping 71 matching lines @@
   ]
   deps = [
     "//base/third_party/dynamic_annotations",
   ]
   if (v8_use_external_startup_data && is_win) {
     public_deps += [ ":gin_v8_snapshot_fingerprint" ]
     deps += [ "//crypto:crypto" ]
     sources += [ "$target_gen_dir/v8_snapshot_fingerprint.cc" ]
     defines += [ "V8_VERIFY_EXTERNAL_STARTUP_DATA" ]
   }
+
+  configs += [ "//v8:external_startup_data" ]
 }
 
 if (v8_use_external_startup_data) {
   action("gin_v8_snapshot_fingerprint") {
     script = "//gin/fingerprint/fingerprint_v8_snapshot.py"
 
     snapshot_file = "$root_build_dir/snapshot_blob.bin"
     natives_file = "$root_build_dir/natives_blob.bin"
     output_file = "$target_gen_dir/v8_snapshot_fingerprint.cc"
 
@@ skipping 71 matching lines @@
     "v8_isolate_memory_dump_provider_unittest.cc",
     "wrappable_unittest.cc",
   ]
 
   deps = [
     ":gin_test",
     "//base/test:test_support",
     "//v8",
   ]
 }