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

chrome/chrome_watcher/BUILD.gn

 # Copyright 2015 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("//chrome/version.gni")
 
 source_set("client") {
   sources = [
     "chrome_watcher_main_api.cc",
     "chrome_watcher_main_api.h",
   ]
   deps = [
     "//base",
   ]
 }
 
 process_version("chrome_watcher_resources") {
   sources = [
     "chrome_watcher.ver",
   ]
   output = "$target_gen_dir/chrome_watcher_version.rc"
 }
 
 shared_library("chrome_watcher") {
   sources = [
-    "$target_gen_dir/chrome_watcher_version.rc",
     "chrome_watcher_main.cc",
   ]
   inputs = [
     "chrome_watcher.def",
   ]
   deps = [
     ":chrome_watcher_resources",
     ":client",
     "//chrome/installer/util",
     "//base",
     "//components/browser_watcher",
   ]
   ldflags = [ "/DEF:" + rebase_path("chrome_watcher.def", root_build_dir) ]
   configs -= [ "//build/config/win:console" ]
   configs += [ "//build/config/win:windowed" ]
 }