[3.12] CI: Fix using `check_source` flags as bool (GH-121848) by webknjaz · Pull Request #121855 · python/cpython

Previously, those flags would sometimes end up having empty string values, which tends to break evaluating them as JSON. This patch adds false fallbacks to all such outputs.

This allows feeding them to fromJSON() without a fear of them causing surprising internal behaviors in the GitHub Actions CI/CD workflows platform itself [1]. The behavior observed was that some skipped jobs wouldn't show up in the workflow sidebar view at all, would display in the graph view as Waiting for pending jobs and in the ${{ needs }} context, they would have a result: failure entry [2].

This should help make PRs like #121831 mergeable again.

(cherry picked from commit a0b205b)