ci: add post-compile success job (#235)

The publish-summary checkrun was used by various automations to trigger
subsequent CI jobs on build success. This step was updated to always run
regardless of build compilation failures making it an unreliable
trigger.
(qualcomm-linux/meta-qcom@e9542ed)

This change adds a success-only job after all compile matrix builds
pass. The resulting check can be reused by downstream workflows.

Imported fro meta-qcom [1].

[1]

qualcomm-linux/meta-qcom@602e6fb

Author: ricardosalveti

.github/workflows/build-yocto.yml

@@ -265,3 +265,10 @@ jobs:
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           pattern: build-url*
+
+  build_successful:
+    needs: compile
+    runs-on: ubuntu-latest
+    steps:
+      - name: Build completed successfully
+        run: echo "All compile matrix jobs succeeded and artifacts uploaded to S3 bucket"