[arpack] Update add_dune_arpackpp_flags to work correctly with the new include directories

cmake/modules/AddARPACKPPFlags.cmake

@@ -14,10 +14,8 @@ function(add_dune_arpackpp_flags _targets)
   if(ARPACKPP_FOUND)
     foreach(_target ${_targets})
       target_link_libraries(${_target} ${ARPACKPP_DUNE_LIBRARIES})
-      get_target_property(_props ${_target} COMPILE_FLAGS)
-      string(REPLACE "_props-NOTFOUND" "" _props "${_props}")
-      set_target_properties(${_target} PROPERTIES COMPILE_FLAGS
-        "${_props} ${ARPACKPP_DUNE_COMPILE_FLAGS} -DENABLE_ARPACKPP=1")
+      target_compile_definitions(${_target} PUBLIC ENABLE_ARPACKPP=1)
+      target_compile_options(${_target} PUBLIC ${ARPACKPP_DUNE_COMPILE_FLAGS})
     endforeach()
   endif()
 endfunction(add_dune_arpackpp_flags)