The error message may also include instructions on how to deal with this. In my case I saw
This script, last modified 2008-01-23, has failed to recognize
the operating system you are using. It is advised that you
download the most up to date version of the config scripts from
http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.guess;hb=HEAD
and
http://git.savannah.gnu.org/gitweb/?p=config.git;a=blob_plain;f=config.sub;hb=HEAD
In a browser I was able to access those files, save them to to my system, and then overwrite the respective ./config/config.guess and ./config/config.sub files in the package being built.