Fuchsia: Adds a script to make a jiri manifest for third_party/pkg stuff
Fuchsia: Adds a script to make a jiri manifest for third_party/pkg stuff

Building the Observatory and the full SDK requires the third_party Dart
packages that we DEPS into a standalone SDK checkout. Fuchsia uses jiri
manifests rather than DEPS files, so this CL adds a script that
translates the DEPS for third_party/pkg stuff into a jiri manifest.

R=asiva@google.com

Review URL: https://codereview.chromium.org/2548173002 .

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