Move rootcling dictionary options after include directories

If ${ARG_OPTIONS} is used to propagate extra include directories to
rootcling and the extra directories contain another ROOT installation,
then ROOT headers will come from the external ROOT and break the build.
We need to make sure that headers from the current build take precedence
over any external installation of ROOT by moving definitions and include
directories towards the beginning of the command line for rootcling.

Author: amadio

cmake/modules/RootNewMacros.cmake

@@ -421,7 +421,7 @@ function(ROOT_GENERATE_DICTIONARY dictionary)
   #---call rootcint------------------------------------------
   add_custom_command(OUTPUT ${dictionary}.cxx ${pcm_name} ${rootmap_name} ${cpp_module_file}
                      COMMAND ${command} -v2 -f  ${dictionary}.cxx ${newargs} ${excludepathsargs} ${rootmapargs}
-                                        ${ARG_OPTIONS} ${definitions} ${includedirs} ${headerfiles} ${_linkdef}
+                                        ${definitions} ${includedirs} ${ARG_OPTIONS} ${headerfiles} ${_linkdef}
                      IMPLICIT_DEPENDS ${_implicitdeps}
                      DEPENDS ${_list_of_header_dependencies} ${_linkdef} ${ROOTCINTDEP} ${ARG_DEPENDENCIES})
   get_filename_component(dictname ${dictionary} NAME)