CLP-1044: Use common slack notification action

[mary-georgiou]

CLP-1044: adopts the shared slack-notify composite action (part of the CLP-894 rollout).

Adds a notify-build-failure job to build.yml that posts to Slack when the build/QA pipeline fails on master, branch-*, or dogfood-*, replacing the previous check_suite-based draft (that trigger never fires for GitHub Actions' own check suites, so the job must live inside the workflow it monitors).

This repo had no prior CI-failure Slack notification, so channel squad-corelang-notifs and branch-patterns: 'master,branch-*,dogfood-*' were chosen to match the repo's actual protected-branch/push triggers in build.yml.

[hashicorp-vault-sonar-prod]

CLP-1044

[gitar-bot]

Code Review ✅ Approved 1 closed / 1 findings

🔴 High risk · The new notification job gains OIDC token issuance permission.

Adopts the shared slack-notify composite action to post build failures to Slack on master, branch-*, and dogfood-* branches. Replaces the previous check_suite-based approach, which never fired for GitHub Actions' own check suites, ensuring notifications are now reliably sent when the build/QA pipeline fails.

✅ 1 closed

✅ Bug: check_suite never fires for GitHub Actions CI, so no alert is ever sent

📄 .github/workflows/slack-notify.yml:3-5 📄 .github/workflows/slack-notify.yml:20-21
This repo's CI runs entirely on GitHub Actions (build.yml), and there is no Cirrus or other external CI config. GitHub documents that the check_suite event "does not trigger workflows if the check suite was created by GitHub Actions or if the check suite's head SHA is associated with GitHub Actions" (this prevents recursive workflows). So when a Build run on master fails, this workflow never starts and nothing gets posted to Slack, which defeats the point of the PR. To fix it, trigger on workflow_run for the Build workflow and read the branch and conclusion from github.event.workflow_run. ReleasabilityCheck.yml already uses workflow_run this way.

Review coverage

🧪 Functional validation 3 of 3 objectives covered

📋 Rules No rules evaluated

🤖 Auto-approval Not enabled · Set up

Implementation Status ✅ 3 of 3 objectives covered

✅ CLP-1044 - 3 of 3 objectives covered

This PR covers adding a CI workflow triggered on check_suite that calls the shared slack notification action to report failures to the #squad-corelang-notifs channel.

✅ 3 covered here

• ✅ Add a CI workflow triggered on check_suite
• ✅ Call the shared slack notification action on master CI failures
• ✅ Report failures to the #squad-corelang-notifs channel

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[sonarqube-next]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
0 Accepted issues

Measures
0 Security Hotspots
0 Dependency risks
No data about Coverage
0.0% Duplication on New Code

See analysis details on SonarQube

[aurelien-coet-sonarsource]

LGTM