target_compile_options is not avaiable in cmake 2.8

cmake/modules/AddIPOptFlags.cmake

@@ -2,7 +2,10 @@ function(add_dune_ipopt_flags _targets)
   if(IPOPT_FOUND)
     cmake_parse_arguments(ADD_DUNE_IPOPT_FLAGS "OBJECT" "" "" ${ARGN})
     foreach(_target ${_targets})
-      target_compile_options(${_target} PRIVATE ${DUNE_IPOPT_CFLAGS})
+      get_target_property(_props ${_target} COMPILE_FLAGS)
+      string(REPLACE "_props-NOTFOUND" "" _props "${_props}")
+      set_target_properties(${_target} PROPERTIES COMPILE_FLAGS
+          "${_props} ${DUNE_IPOPT_CFLAGS}")
       if(NOT ADD_DUNE_IPOPT_FLAGS_OBJECT)
         target_link_libraries(${_target} ${IPOPT_LIBRARY})
       endif()