Ability to supply product flavor for react-native run-android command

Summary:This small update to runAndroid.js allows to specify product flavor as optional argument, like that:
`react-native run-android --option-flavor=staging`

This option is useful when developing complex applications that require some flavor-specific functionality. More information about productFlavors can be found here: http://developer.android.com/intl/ru/tools/building/configuring-gradle.html
Closes #6010

Differential Revision: D3011662

Pulled By: mkonicek

fb-gh-sync-id: ce730a17340c1f21b5d75f28a784db4d6fd99725
shipit-source-id: ce730a17340c1f21b5d75f28a784db4d6fd99725

local-cli/runAndroid/runAndroid.js

@@ -34,6 +34,10 @@ function _runAndroid(argv, config, resolve, reject) {
     command: 'root',
     type: 'string',
     description: 'Override the root directory for the android build (which contains the android directory)',
+  }, {
+    command: 'flavor',
+    type: 'string',
+    required: false,
   }], argv);
 
   args.root = args.root || '';
@@ -70,7 +74,15 @@ function buildAndRun(args, reject) {
       ? 'gradlew.bat'
       : './gradlew';
 
-    const gradleArgs = ['installDebug'];
+    const gradleArgs = [];
+    if (args['flavor']) {
+        gradleArgs.push('install' +
+          args['flavor'][0].toUpperCase() + args['flavor'].slice(1)
+        );
+    } else {
+        gradleArgs.push('installDebug');
+    }
+
     if (args['install-debug']) {
       gradleArgs.push(args['install-debug']);
     }