Currently 'run_task' tasks have no easy way to depend on a build task. For example, some
python unittests need a Firefox binary for their tests, like the mozrunner tests and future
test harness selftests (like mochitest tests).
This patch allows kinds to add a new key to the kind config which maps test platforms to
build-labels. Then 'run_task' jobs can add a 'requires-build': true field to get a build
dependency automatically added. The build artifact url will also be stored in the
$GECKO_INSTALLER_URL environment variable on the test host.
MozReview-Commit-ID: Jqyhbj7nC6z
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extra : rebase_source : 2f44b6c94f35a0d2e11464cf773e821ae6fe8538