[analyzer] Fix bugs in generate_files script.
[analyzer] Fix bugs in generate_files script.

- task_dependency_graph no longer exists.
- summary/generate.dart expects an IDL file, it fails
  when run without any args. There's only one such
  file in the repo so I passed that.

Change-Id: I63854acc070c1cf4c49bb82d03f1312930e447e5
Tested: Ran the script, it generates all files without errors.
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/255481
Reviewed-by: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>
Commit-Queue: Brian Wilkerson <1f7641b6b14c52b9163524ab8d9aabff80176f21@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk