Fix SpotBugs - run build task with JDK 11 too

SpotBugs runs as part of the 'build' task, not just in the explicit
SpotBugs step. Updated the build step to also use JDK_11 since
SpotBugs 4.9.2 requires Java 11+.

Co-authored-by: torosent <[email protected]>

Author: Copilot

.github/workflows/build-validation.yml

@@ -42,7 +42,9 @@ jobs:
       uses: gradle/gradle-build-action@v2
 
     - name: Build with Gradle
-      run: ./gradlew build -x test
+      run: |
+        export JAVA_HOME=$JDK_11
+        ./gradlew build -x test
     
     - name: Run SpotBugs
       run: |