Bug 1314136 - ship PGP public key alongside nightly builds. r=releng-reviewers,aki DONTBUILD

Bug 1713258 added KEY to the beetmover manifest, but it gets excluded
from `upstreamArtifacts` in `generate_beetmover_upstream_artifacts`
because it's not in the signing task's `release-artifacts` attribute,
and so it doesn't actually work.

Differential Revision: https://phabricator.services.mozilla.com/D132470

taskcluster/gecko_taskgraph/transforms/signing.py

@@ -182,6 +182,9 @@ def make_task_description(config, jobs):
         if dep_job.kind in task["dependencies"]:
             task["if-dependencies"] = [dep_job.kind]
 
+        if "linux" in build_platform:
+            task["release-artifacts"] = ["public/build/KEY"]
+
         if "macosx" in build_platform:
             shippable = "false"
             if "shippable" in attributes and attributes["shippable"]: