ci: fail when we cannot get the computed library version (#15326)

## Description

This is failing in CI sometimes, where we cannot get the artifact
(unclear why), but it is causing issues for the s3 publish job instead
of the compute job being the one which fails.

## Testing

<!-- Describe your testing strategy or note what tests are included -->

## Risks

<!-- Note any risks associated with this change, or "None" if no risks
-->

## Additional Notes

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Author: brettlangdon

.gitlab/download-library-version-from-gh-actions.sh

@@ -18,4 +18,9 @@ while [ $(date +%s) -lt $end_time ]; do
   sleep 30
 done
 
+if [ ! -f "library-version/version.txt" ]; then
+  echo "Failed to download library version artifact from GitHub Actions"
+  exit 1
+fi
+
 echo "Library Version: $(cat library-version/version.txt)"

.gitlab/package.yml

@@ -6,6 +6,8 @@ compute_library_version:
     DDOCTOSTS_ID_TOKEN:
       aud: dd-octo-sts
   script: |
+    set -eo pipefail
+
     if [ -z ${GH_TOKEN} ]
     then
       # Use dd-octo-sts to get GitHub token