Mark org.apache.ant:ant as optional=true

ant is not required for usage of cglib, hence should be marked as optional.
Related to spring-projects/spring-boot#10137 (comment)

Author: ceefour

cglib/pom.xml

@@ -64,6 +64,7 @@
         <dependency>
             <groupId>org.apache.ant</groupId>
             <artifactId>ant</artifactId>
+            <optional>true</optional>
         </dependency>
 
         <dependency>