Fix ewt_manifest.gyp to support both target and host toolchains

base/trace_event/etw_manifest/etw_manifest.gyp

 # 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.
 {
   'targets': [
     {
       # GN version: //base/trace_event/etw_manifest/BUILD.gn
       'target_name': 'etw_manifest',
       'type': 'static_library',
+      'toolsets': ['host', 'target'],
       'conditions': [
         ['OS=="win"', {
           'sources': [
             'chrome_events_win.man',
           ],
           'variables': {
             'man_output_dir': '<(SHARED_INTERMEDIATE_DIR)/base/trace_event/etw_manifest',
           },
           'rules': [{
             # Rule to run the message compiler.
@@ skipping 10 matching lines @@
               '-um',
               '<(RULE_INPUT_PATH)',
             ],
             'message': 'Running message compiler on <(RULE_INPUT_PATH)',
           }],
         }],
       ],
     }
   ]
 }