Only process build results once (#133)

On long-lived machines, it's possible that the `.build-results` directory isn't cleared between invocations. This will result in the job summary including results from previous jobs.

By marking each build-results file as 'processed' at the end of the job, we can avoid this scenario.

.github/workflows/demo-job-summary.yml

@@ -16,6 +16,10 @@ jobs:
         npm install
         npm run build
       working-directory: sources
+    - uses: actions/setup-java@v4
+      with:
+        distribution: 'temurin'
+        java-version: '11'
     - name: Setup Gradle
       uses: ./setup-gradle
     - name: Build kotlin-dsl project