[VM] Avoid deadlock by allowing us to run kernel isolate from a script snapshot, fixes all dartk-sim* builders
[VM] Avoid deadlock by allowing us to run kernel isolate from a script snapshot, fixes all dartk-sim* builders

Currently on sim* architectures we use a script snapshot (and not an app
jit snapshot, as we normally do) for the kernel isolate.
  -> See utils/application_snapshot.gni:declare_args()

The change in [0] causes a deadlock where we try to compile the kernel
isolate (or rather a script snapshot of it) via the kernel isolate.

This CL fixes all the dartk-sim* builders by allowing us to run the
kernel snapshot from a script snapshot.

[0] https://dart-review.googlesource.com/52986

Change-Id: I513993f7c78310165d90f7622879482598f1e577
Reviewed-on: https://dart-review.googlesource.com/53380
Reviewed-by: Vyacheslav Egorov <72c81f38df725d8f1832acb9b5bb99563fc2f1b9@google.com>

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