title: How to change the location of classes generated by MapStruct?
body: <p>I am using MapStruct to generate the mapping between the JAXB classes and my domain classes. 
  I am using gradle plugin as described in MapStruct official site. During the compilation process, the classes are generated in "build/generated/sources/apt/main".
  How can i change this location? I am not able to find any guide for gradle though there is a compiler flag to change it through ant script, but unfortunately it is not working for gradle
  Any help is appreciated. </p>