Update RootMacros.cmake

Allow dictionary files to be created in subdirectories. This was working earlier and is broken now. As there is no way to define othe output directory, providing the dictionary with path is the only way to achieve that.

cmake/modules/RootMacros.cmake

@@ -659,6 +659,7 @@ function(ROOT_GENERATE_DICTIONARY dictionary)
     target_include_directories(${dictionary} PRIVATE
       ${incdirs} $<TARGET_PROPERTY:${ARG_MODULE},INCLUDE_DIRECTORIES>)
   else()
+    get_filename_component(dictionary_name ${dictionary} NAME)   
     add_custom_target(${dictionary} DEPENDS ${dictionary}.cxx ${pcm_name} ${rootmap_name} ${cpp_module_file})
   endif()