Fix --compile_all flag (--compile-all is wrong)

runtime/observatory/tests/service/malformed_test.dart

Index: runtime/observatory/tests/service/malformed_test.dart
diff --git a/runtime/observatory/tests/service/malformed_test.dart b/runtime/observatory/tests/service/malformed_test.dart
index 3d22471925b3c75fba9ecddae5abc7170eb4a5e3..6cf5302c49e06061c7f0297f22f1abf127029fc0 100644
--- a/runtime/observatory/tests/service/malformed_test.dart
+++ b/runtime/observatory/tests/service/malformed_test.dart
@@ -1,7 +1,7 @@
 // Copyright (c) 2014, 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.
-// VMOptions=--compile-all --error_on_bad_type --error_on_bad_override
+// VMOptions=--compile_all --error_on_bad_type --error_on_bad_override
 
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';