Add support for building the Dart VM for Android OS.

runtime/dart-runtime.gyp

 # Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 # for details. All rights reserved. Use of this source code is governed by a
 # BSD-style license that can be found in the LICENSE file.
 
 {
   'includes': [
     'vm/vm.gypi',
     'bin/bin.gypi',
     'third_party/double-conversion/src/double-conversion.gypi',
     'third_party/jscre/jscre.gypi',
@@ skipping 46 matching lines @@
         'vm/debugger_api_impl.cc',
       ],
       'defines': [
         'DART_SHARED_LIB',
       ],
       'direct_dependent_settings': {
         'include_dirs': [
           'include',
         ],
       },
+      'conditions': [
+       ['dart_want_separate_host_toolset==1', {
+              'toolsets': ['host'],
+            }, {
+              'toolsets': ['target'],
+            }],
+      ],
     },
   ],
 }