prevent xercesc from being linked when no xml support is required

Former-commit-id: 63bf3c1a71

CMakeLists.txt

@@ -521,6 +521,7 @@ endif(ENABLE_MSAT)
 ##
 #############################################################
 
+if(STORM_SUPPORT_XML_INPUT_FORMATS)
     find_package(Xerces)
     if(NOT XERCES_FOUND)
             message(STATUS "Use shipped version of xerces")
@@ -535,6 +536,7 @@ if(STORM_HAVE_XERCES)
             include_directories(${XERCESC_INCLUDE})
             list(APPEND STORM_LINK_LIBRARIES ${XERCESC_LIBRARIES})
     endif()
+endif()
 
 #############################################################
 ##