The `add_noarch` option of `get_valid_arches` is broken and doesn't
really do anything (noarch is always present in the result).
This causes packages that have ExclusiveArch including noarch to
actually not be excluded. They should be.
Changing this globally could have a very big impact. Therefore we can
hide it behind a configuration option so that it's opt-in.
JIRA: COMPOSE-2457
Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>
a4bbf475f1