Merge pull request #34 from bazelbuild:Add-step-to-test-Downstream-builds

PiperOrigin-RevId: 336285141
Change-Id: I51362d32bfce1349323c972ccd87a3d73c1c0151

Author: copybara-github

docs/release.md

@@ -40,6 +40,10 @@ with the new release candidates. See
 [#8302](https://github.com/bazelbuild/bazel/pull/8302) as an example.
 The PR triggers the CI presubmit.
 
+
+6. Trigger a new build on Downstream https://buildkite.com/bazel/bazel-at-head-plus-downstream.
+   Using `pulls/PRNUMBER/head` for the branch.
+
     1. If the CI finishes successfully:
         - create the release artifacts from the
         release candidate: