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

runtime/observatory/tests/service/inbound_references_test.dart

 // 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
 
 library inbound_references_test;
 
 import 'package:observatory/service_io.dart';
 import 'package:unittest/unittest.dart';
 import 'test_helper.dart';
 
 class Node {
   var edge;
 }
@@ skipping 32 matching lines @@
                          r['source'].clazz.name=='Node');
     hasReferenceSuchThat((r) => r['slot'] == 1 &&
                          r['source'].isList);
     hasReferenceSuchThat((r) => r['slot']=='<unknown>' &&
                          r['source'] is Field);
   }
 
 ];
 
 main(args) => runIsolateTests(args, tests, testeeBefore: script);