Add configurations for prebuilt iOS and iOS simulator targets

packages/flutter_tools/lib/src/application_package.dart

@@ -98,13 +98,11 @@ class ApplicationPackageStore {
 
         case TargetPlatform.iOS:
           assert(iOS == null);
-          assert(config.type != BuildType.prebuilt);
           iOS = new IOSApp(localPath: path.join(config.buildDir, IOSApp._defaultName));
           break;
 
         case TargetPlatform.iOSSimulator:
           assert(iOSSimulator == null);
-          assert(config.type != BuildType.prebuilt);
           iOSSimulator = new IOSApp(localPath: path.join(config.buildDir, IOSApp._defaultName));
           break;
 

packages/flutter_tools/lib/src/runner/flutter_command_runner.dart

@@ -226,6 +226,18 @@ class FlutterCommandRunner extends CommandRunner {
           testable: true
         ));
       }
+
+      if (hostPlatform == HostPlatform.mac) {
+        configs.add(new BuildConfiguration.prebuilt(
+          hostPlatform: HostPlatform.mac,
+          targetPlatform: TargetPlatform.iOS
+        ));
+
+        configs.add(new BuildConfiguration.prebuilt(
+          hostPlatform: HostPlatform.mac,
+          targetPlatform: TargetPlatform.iOSSimulator
+        ));
+      }
     } else {
       if (!FileSystemEntity.isDirectorySync(enginePath))
         logging.warning('$enginePath is not a valid directory');