dd4hep_add_dictionary: use temporary files to create Dictionaries

because add_custom_command does not know the COMPILE_LANGUAGE we are not allowed to treat definitions with that genex inside.
We cannot use add_custom_command(TARGET because that fails with the same error, even though it maybe shouldn't

For compatibility with ninja(?) we need to use these $<CONFIG>$<COMPILE_LANGUAGE> shenanigans

add USE_COMMAND_FOR_GENERATION to fall back to old way