Fix test expectations for run-fork JVM args on Java 13+

Closes gh-17008

spring-boot-project/spring-boot-tools/spring-boot-maven-plugin/src/it/run-fork/verify.groovy

+import java.lang.reflect.Method;
+
 import static org.junit.Assert.assertTrue
 
+def boolean isJava13OrLater() {
+	for (Method method : String.class.getMethods()) {
+		if (method.getName().equals("stripIndent")) {
+			return true;
+		}
+	}
+	return false;
+}
+
 def file = new File(basedir, "build.log")
 assertTrue file.text.contains("I haz been run from '$basedir'")
-assertTrue file.text.contains("JVM argument(s): -Xverify:none -XX:TieredStopAtLevel=1")
-
+if (isJava13OrLater()) {
+	assertTrue file.text.contains("JVM argument(s): -XX:TieredStopAtLevel=1")
+}
+else {
+	assertTrue file.text.contains("JVM argument(s): -Xverify:none -XX:TieredStopAtLevel=1")
+}