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

media/cdm/ppapi/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/config/features.gni")
 import("//chrome/version.gni")  # TODO layering violation!
 import("//media/cdm/ppapi/cdm_adapter.gni")
 
 # Android doesn't use ffmpeg.
 use_ffmpeg = !is_android
@@ skipping 31 matching lines @@
       "external_clear_key/ffmpeg_cdm_video_decoder.cc",
       "external_clear_key/ffmpeg_cdm_video_decoder.h",
     ]
     defines += [ "CLEAR_KEY_CDM_USE_FFMPEG_DECODER" ]
     deps += [ "//third_party/ffmpeg" ]
   }
 
   # TODO(GYP) on Mac: 'DYLIB_INSTALL_NAME_BASE': '@loader_path',
 }
 
-clearkeycdmadapter_rc_file = "$target_gen_dir/clearkeycdmadapter_version.rc"
-
 process_version("clearkeycdmadapter_resources") {
   visibility = [ ":*" ]
   sources = [
     "//media/clearkeycdmadapter.ver",
     "external_clear_key/BRANDING",
   ]
-  output = clearkeycdmadapter_rc_file
+  output =  "$target_gen_dir/clearkeycdmadapter_version.rc"
 }
 
 cdm_adapter("clearkeycdmadapter") {
-  sources = [
-    clearkeycdmadapter_rc_file,
-  ]
-
   # Check whether the plugin's origin URL is valid.
   defines = [ "CHECK_DOCUMENT_URL" ]
   deps = [
     ":clearkeycdm",
     ":clearkeycdmadapter_resources",
     "//ppapi/cpp",
   ]
 
   if (is_posix && !is_mac && enable_pepper_cdms) {
     # Because clearkeycdm has type 'loadable_module', we must explicitly
     # specify this dependency.
     ldflags = [ rebase_path("$root_out_dir/libclearkeycdm.so", root_build_dir) ]
     libs = [ "rt" ]
   }
 }