7fcff7e87f
Also redirects usage warnings to stderr, adds --help, and verifies that the sdk you pass in actually supports NNBD. Change-Id: Ia758f69648f88108b3c0df9de46ab246d3db0c9e Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/127202 Reviewed-by: Konstantin Shcheglov <scheglov@google.com> Reviewed-by: Mike Fairhurst <mfairhurst@google.com> Reviewed-by: Brian Wilkerson <brianwilkerson@google.com> Commit-Queue: Janice Collins <jcollins@google.com>