Ensure ordered DRA artifacts

As things are now we allow parallel builds on the
packaging pipeline, which would result in out of order
artifacts (depending on which one takes longer to finish).

This commit leverages a queue to ensure a FIFO queue
for DRA artifacts.

.buildkite/packaging.pipeline.yml

@@ -1,6 +1,11 @@
 # yaml-language-server: $schema=https://raw.githubusercontent.com/buildkite/pipeline-schema/main/schema.json
 # TODO: Pre-cache beats-dev/golang-crossbuild container image
 
+# prevent out of order DRA publishing
+# otherwise commits in quick succession will run in parallel and possibly result in our of order DRA artifacts
+agents:
+  queue: "dra-builder-queue"
+
 env:
   ASDF_MAGE_VERSION: 1.15.0
   AWS_ARM_INSTANCE_TYPE: "m6g.xlarge"