Add support for building the Dart VM for Android OS.

dart.gyp

Index: dart.gyp
diff --git a/dart.gyp b/dart.gyp
index 1b62e45af165c3358b8180c1af485ce725034bdf..980a59c673db19d2fc6b7b171f6bc096d5a42ddb 100644
--- a/dart.gyp
+++ b/dart.gyp
@@ -21,6 +21,13 @@
         'runtime/dart-runtime.gyp:process_test',
         'runtime/dart-runtime.gyp:test_extension',
       ],
+      'conditions': [
+        ['dart_want_separate_host_toolset==1', {
+          'toolsets': ['host'],
+        }, {
+          'toolsets': ['target'],
+        }],
+      ]
     },
     {
       # Build the SDK. This target is separate from upload_sdk as the
@@ -66,6 +73,11 @@
             'compiler',
           ],
         }],
+        ['dart_want_separate_host_toolset==1', {
+            'toolsets': ['host'],
+          }, {
+            'toolsets': ['target'],
+          }],
       ],
     },
     {
@@ -93,6 +105,13 @@
           ],
         },
       ],
+      'conditions': [
+          ['dart_want_separate_host_toolset==1', {
+            'toolsets': ['host'],
+          }, {
+            'toolsets': ['target'],
+          }],
+      ],
     },
     {
       'target_name': 'dart2js',
@@ -100,6 +119,13 @@
       'dependencies': [
         'utils/compiler/compiler.gyp:dart2js',
       ],
+      'conditions': [
+          ['dart_want_separate_host_toolset==1', {
+            'toolsets': ['host'],
+          }, {
+            'toolsets': ['target'],
+          }],
+      ],
     },
     {
       'target_name': 'api_docs',
@@ -107,6 +133,13 @@
       'dependencies': [
         'utils/apidoc/apidoc.gyp:api_docs',
       ],
+      'conditions': [
+          ['dart_want_separate_host_toolset==1', {
+            'toolsets': ['host'],
+          }, {
+            'toolsets': ['target'],
+          }]
+    ],
     }
   ],
 }