Fix regression: report size delta size on PR.

The necessary steps have in fact been documented here: https://github.com/arduino/report-size-deltas/blob/main/docs/FAQ.md#workflow-triggered-by-pull_request-event but I have overlooked them when I fixed the upload issue. With this PR the size deltas are - once again - reported within the PR.

.github/workflows/compile-examples.yml

@@ -13,7 +13,7 @@ on:
       - "src/**"
 
 jobs:
-  build:
+  compile:
     runs-on: ubuntu-latest
 
     env:
@@ -283,18 +283,28 @@ jobs:
           enable-deltas-report: "true"
           sketches-report-path: ${{ env.SKETCHES_REPORTS_PATH }}
 
-      - name: Write data to size trends report spreadsheet
-        # Update report on every push to the master branch
-        if: github.event_name == 'push' && github.ref == 'refs/heads/master'
-        uses: arduino/report-size-trends@main
-        with:
-          sketches-report-path: ${{ env.SKETCHES_REPORTS_PATH }}
-          google-key-file: ${{ secrets.GOOGLE_KEY_FILE }}
-          spreadsheet-id: 1I6NZkpZpf8KugBkE92adB1Z3_b7ZepOpCdYTOigJpN4
-
+      # This step is needed to pass the size data to the report job.
       - name: Save memory usage change report as artifact
         if: github.event_name == 'pull_request'
         uses: actions/upload-artifact@v4
         with:
           name: sketches-report-${{ matrix.board.artifact-name-suffix }}
           path: ${{ env.SKETCHES_REPORTS_PATH }}
+
+  # When using a matrix to compile for multiple boards, it's necessary to use a separate job for the deltas report
+  report:
+    needs: compile # Wait for the compile job to finish to get the data for the report
+    if: github.event_name == 'pull_request' # Only run the job when the workflow is triggered by a pull request
+    runs-on: ubuntu-latest
+
+    steps:
+      # This step is needed to get the size data produced by the compile jobs
+      - name: Download sketches reports artifacts
+        uses: actions/download-artifact@v4
+        with:
+          # All workflow artifacts will be downloaded to this location.
+          path: ${{ env.SKETCHES_REPORTS_PATH }}
+
+      - uses: arduino/report-size-deltas@v1
+        with:
+          sketches-reports-source: ${{ env.SKETCHES_REPORTS_PATH }}

.gitignore

@@ -5,3 +5,4 @@
 *.orig
 .vs
 build
+.idea/