Fix path to flutter_tester when using local enginde on Mac OS (#11134)

diff --git a/packages/flutter_tools/lib/src/artifacts.dart b/packages/flutter_tools/lib/src/artifacts.dart
index c66241d..565ce34 100644
--- a/packages/flutter_tools/lib/src/artifacts.dart
+++ b/packages/flutter_tools/lib/src/artifacts.dart
@@ -224,7 +224,7 @@
     if (getCurrentHostPlatform() == HostPlatform.linux_x64) {
       return fs.path.join(engineOutPath, _artifactToFileName(Artifact.flutterTester));
     } else if (getCurrentHostPlatform() == HostPlatform.darwin_x64) {
-      return fs.path.join(engineOutPath, 'FlutterTester.app', 'Contents', 'MacOS', 'FlutterTester');
+      return fs.path.join(engineOutPath, 'flutter_tester');
     }
     throw new Exception('Unsupported platform $platform.');
   }