conditional gradle execution

Author: steven-blakowski

.github/workflows/samples-java-client-jdk11.yaml

@@ -132,5 +132,5 @@ jobs:
 
       - name: Build with Gradle
         working-directory: ${{ matrix.sample }}
-        if: ${{ exists('./gradlew') }}
+        if: ${{ hashFiles('./gradlew') != '' }}
         run: ./gradlew build -x test