workflow: Add check-main-status workflow

The workflow checks the result of check runs on the latest commit on
the main branch. When checks on main are failing or pending the
workflow will fail. This prevents introducing more potenisal issues
when main is already broken.

To skip the check when making a fix for main, add the fix-ci label to
the PR.

Signed-off-by: Gregers Gram Rygg <gregers.gram.rygg@nordicsemi.no>

.github/workflows/check-main-status.yml

@@ -0,0 +1,68 @@
+name: Check Main Branch Status
+on:
+  pull_request:
+  workflow_dispatch:
+    inputs:
+      pr_number:
+        description: "Pull Request number"
+        required: true
+
+jobs:
+  check-main-status:
+    runs-on: ubuntu-24.04
+    env:
+      PR_NUMBER: ${{ github.event.number || github.event.inputs.pr_number }}
+    steps:
+      - name: Check if PR has 'fix-ci' label
+        id: has_fix_ci_label
+        uses: actions/github-script@v7
+        with:
+          retries: 3
+          script: |
+            const labels = await github.rest.issues.listLabelsOnIssue({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              issue_number: process.env.PR_NUMBER,
+            });
+
+            const hasFixCiLabel = labels.data.map(label => label.name).includes('fix-ci');
+            console.log(`Has 'fix-ci' label: ${hasFixCiLabel}`);
+
+            return hasFixCiLabel;
+
+      - name: Ensure Main Branch Check Runs Are Successful
+        if: ${{ steps.has_fix_ci_label.outputs.result == 'false' }}
+        uses: actions/github-script@v7
+        with:
+          retries: 3
+          script: |
+            const mainRef = await github.rest.git.getRef({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              ref: 'heads/main',
+            });
+
+            const mainSha = mainRef.data.object.sha;
+            console.log(`Main branch SHA: ${mainSha}`);
+
+            const checkRuns = await github.rest.checks.listForRef({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              ref: mainSha,
+            });
+
+            console.log(`Check runs (${checkRuns.data.total_count}):`);
+            for (let run of checkRuns.data.check_runs) {
+              console.log(`- ${run.name}: ${run.conclusion}`);
+            }
+
+            const failedChecks = checkRuns.data.check_runs.filter(run => run.conclusion === 'failure');
+            const pendingChecks = checkRuns.data.check_runs.filter(run => run.status !== 'completed');
+
+            if (failedChecks.length > 0) {
+              core.setFailed('Cannot merge: The main branch has failing checks.');
+            } else if (pendingChecks.length > 0) {
+              core.setFailed('Checks for main branch are pending. Please try again later.');
+            } else {
+              console.log('Main branch is healthy.');
+            }