Add simple native formatting test

As discussed in #1327 a very simple formatting test is added to the native build.

It's a fairly basic smoke test, but I actually verified here EvaristeGalois11#1 that it's enough to catch problems like the recent bug 😁

Fixes #1331

COPYBARA_INTEGRATE_REVIEW=#1331 from EvaristeGalois11:native-test 04b4238
PiperOrigin-RevId: 866015724

Author: EvaristeGalois11

util/HelloWorld.java

@@ -0,0 +1,19 @@
+/*
+ * Copyright 2026 Google Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
+ * in compliance with the License. You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software distributed under the License
+ * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
+ * or implied. See the License for the specific language governing permissions and limitations under
+ * the License.
+ */
+
+class HelloWorld {
+  public static void main(String[] args) {
+    System.out.println("Hello, World!");
+  }
+}

util/test-native.sh

@@ -28,3 +28,5 @@ if [[ $status -ne 2 ]]; then
   echo "google-java-format_linux (native) without arguments should have printed usage help and exited with 2, but did not :("
   exit 1
 fi
+
+core/target/google-java-format util/HelloWorld.java