ci(pr_test_build_images): Bind the step varable

Author: NickLarsenNZ

.github/workflows/pr_test_build_images.yaml

@@ -19,6 +19,8 @@ jobs:
       - uses: actions/checkout@692973e3d937129bcbf40652eb9f2f61becf3332 # v4.1.7
       - id: shard
         shell: bash
+        env:
+          GITHUB_DEBUG: ${{ runner.debug }}
         run: |
           set -euo pipefail
           [ -n "$GITHUB_DEBUG" ] && set -x