Bug 1372510 - Exclude 'job' tasks that require a build from the default try selection, r=dustin

It's a bit hacky to single out 'build' dependencies, but most tasks have a dependency on a docker
image, so we can't blanket skip all 'job' tasks with any dependencies at all. This is far from ideal
but is an improvement on the current behaviour of running build dependencies all the time, even if
the 'job' task gets optimized away.

There is likely a cleverer solution, but that can be follow-up work.

MozReview-Commit-ID: 6T68LT5VSrg

taskcluster/taskgraph/target_tasks.py

@@ -54,7 +54,7 @@ def target_tasks_try_option_syntax(full_task_graph, parameters):
     parameters['message'] and, for context, the full task graph."""
     options = try_option_syntax.TryOptionSyntax(parameters['message'], full_task_graph)
     target_tasks_labels = [t.label for t in full_task_graph.tasks.itervalues()
-                           if options.task_matches(t.attributes)]
+                           if options.task_matches(t)]
 
     attributes = {
         k: getattr(options, k) for k in [