Disable dependency_graph_test on some platforms.
Disable dependency_graph_test on some platforms.

Do to reorganizing some code, it now transitively imports mirrors, so
don't run it on platforms that don't have mirrors.

We only really care about this test on the standalone VM anyway.

R=efortuna@google.com

Review-Url: https://codereview.chromium.org/2930153002 .

dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-archive/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dart-archive/dart-sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk,dart-lang/sdk,dartino/dart-sdk