Update post-merge workflow to add 'needs: analysis' label (#39277)

.github/workflows/pull-request-post-merge-processing.yml

@@ -45,3 +45,9 @@ jobs:
               env:
                   PULL_REQUEST_ID: ${{ github.event.pull_request.node_id }}
                   GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+            - name: 'Add the label for PR analysis'
+              if: github.event.pull_request.base.ref == 'trunk'
+              uses: actions-ecosystem/action-add-labels@bd52874380e3909a1ac983768df6976535ece7f8
+              with:
+                github_token: ${{ secrets.GITHUB_TOKEN }}
+                labels: 'needs: analysis'