DBC: Adds simdbc64 target, adds arm64 arithmetic overflow logic

tools/testing/dart/runtime_configuration.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.
 
 library runtime_configuration;
 
 import 'compiler_configuration.dart' show CommandArtifact;
 
 // TODO(ahe): Remove this import, we can precompute all the values required
 // from TestSuite once the refactoring is complete.
@@ skipping 154 matching lines @@
       case 'simarm':
       case 'arm':
       case 'simarmv6':
       case 'armv6':
       case ' simarmv5te':
       case 'armv5te':
       case 'simmips':
       case 'mips':
       case 'simarm64':
       case 'simdbc':
+      case 'simdbc64':
         multiplier *= 4;
         break;
     }
     if (mode == 'debug') {
       multiplier *= 2;
     }
     return multiplier;
   }
 }
 
@@ skipping 87 matching lines @@
 class DummyRuntimeConfiguration extends DartVmRuntimeConfiguration {
   List<Command> computeRuntimeCommands(
       TestSuite suite,
       CommandBuilder commandBuilder,
       CommandArtifact artifact,
       List<String> arguments,
       Map<String, String> environmentOverrides) {
     throw "Unimplemented runtime '$runtimeType'";
   }
 }