Some options in config_example.py are not reachable. It makes users
confused. So make the options in the file as gobal_alias.
Signed-off-by: zhizhou.zhang <zhizhou.zhang@spreadtrum.com>
list_or_* functions (e.g. list_or_string) will now always return a list,
however will accept lists or indivitual values. Also added a list_or()
generator function, similar to what already exists for list_of().