Add support for building the Dart VM for Android OS.

tools/gyp/configurations.gypi

 # Copyright (c) 2012, 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.
 
 {
   'variables': {
     'common_gcc_warning_flags': [
       '-Wall',
       '-Wextra', # Also known as -W.
       '-Wno-unused-parameter',
       # TODO(v8-team): Fix V8 build.
       #'-Wold-style-cast',
     ],
 
     # Default value.  This may be overridden in a containing project gyp.
     'target_arch%': 'ia32',
 
     # Don't use separate host toolset for compiling V8.
     'want_separate_host_toolset': 0,
 
+    # Optionally use separate host toolset for compiling dart.
+    'dart_want_separate_host_toolset': 0,
+
+  'conditions': [
+      [ 'OS=="android"', { 'dart_want_separate_host_toolset': 1}]
+  ],
+
   'conditions': [
     ['"<(target_arch)"=="ia32"', { 'dart_target_arch': 'IA32', }],
     ['"<(target_arch)"=="x64"', { 'dart_target_arch': 'X64', }],
     ['"<(target_arch)"=="arm"', { 'dart_target_arch': 'ARM', }],
     ['"<(target_arch)"=="simarm"', { 'dart_target_arch': 'SIMARM', }],
   ],
   },
   'conditions': [
     [ 'OS=="linux"', { 'includes': [ 'configurations_make.gypi', ], } ],
     [ 'OS=="mac"', { 'includes': [ 'configurations_xcode.gypi', ], } ],
@@ skipping 86 matching lines @@
       'Debug': {
         'inherit_from': ['Debug<(dart_target_arch)']
       },
 
       'Release': {
         'inherit_from': ['Release<(dart_target_arch)']
       },
     },
   },
 }