Add a GN flag for the Windows multi-dll build.

chrome/chrome_repack_locales.gni

 # 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/config/chrome_build.gni")
 import("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//tools/grit/repack.gni")
 
 # Arguments:
 #
 #   locale
 #       Internal name of locale. e.g. "pt-BR"
 #
 #   output
@@ skipping 138 matching lines @@
   }
 
   # The group that external targets depend on which collects all deps.
   group(group_target_name) {
     if (defined(invoker.visibility)) {
       visibility = invoker.visibility
     }
     deps = locale_targets
   }
 }