Release automation fixes (#276)

* Automation script must be executable
* Test BCR tests with both Bazel 8.x and 7.x, as suggested by @fmeum in discussion of https://github.com/bazelbuild/bazel-central-registry/pull/3654
diff --git a/.bcr/presubmit.yml b/.bcr/presubmit.yml
index fc98575..b404525 100644
--- a/.bcr/presubmit.yml
+++ b/.bcr/presubmit.yml
@@ -6,6 +6,7 @@
   - windows
   bazel:
   - 8.x
+  - 7.x
 tasks:
   verify_targets:
     name: Verify build targets
diff --git a/.github/workflows/create_archive_and_notes.sh b/.github/workflows/create_archive_and_notes.sh
old mode 100644
new mode 100755