minor change

build.gradle

@@ -66,7 +66,7 @@ distributions.main.contents {
                 version: project.version,
                 date: date.format('yyyy-MM-dd'),
                 copyright: date.format('yyyy'),
-                javaCompatibility: sourceCompatibility.toString(),
+                javaCompatibility: compileJava.options.release.get().toString(),
                 appName: project.name,
                 citygml4jVersion: citygml4jVersion
         ])