Adds arch_dependent key to the task section of trigger config file. if set to True, the jobrunner will instruct Buildbot to select a builder tagged with the specified architecture. 'noarch' is used otherwise.

From what I gather based on the current Buildbot configuration ( https://pagure.io/fedora-qa/qa-ansible/blob/qa-master/f/roles/taskotron/buildmaster-configure/templates/taskotron.master.cfg.j2#_78 and following lines), this is already "accidentally enabled", but I'd like to have a second opinion on that.
I also made a guesstimate on which key is used to tell buildbot which Builder to use - see lines 59/60 of the runners.py diff