Remove ash_unittests/mash_unittests from Windows build targets

ash/mus/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("//build/config/ui.gni")
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//services/service_manager/public/cpp/service.gni")
 import("//services/service_manager/public/service_manifest.gni")
 import("//tools/grit/repack.gni")
 
+assert(is_chromeos)
+
 source_set("lib") {
   sources = [
     "accelerators/accelerator_controller_delegate_mus.cc",
     "accelerators/accelerator_controller_delegate_mus.h",
     "accelerators/accelerator_controller_registrar.cc",
     "accelerators/accelerator_controller_registrar.h",
     "accelerators/accelerator_handler.h",
     "accelerators/accelerator_ids.h",
     "accessibility_delegate_mus.cc",
     "accessibility_delegate_mus.h",
@@ skipping 260 matching lines @@
     "//ui/views/mus",
   ]
 
   data_deps = [
     ":mus",
     "//mash/quick_launch",
   ]
 
   defines = [ "NOTIMPLEMENTED_POLICY=5" ]
 }