Defines for detecting build OS?

[Greg_Swift at aotx.uscourts.gov]

> I am not sure it you are seeing spec file born for the "SUSE build
> system". But if yes the list you are looking is described here for
example:
>
> http://en.opensuse.org/Build_Service/cross_distribution_package_how_to

thats kewl and a handy link, thanks... it would be nice if this was more
standardized because I've yet to see %{rhel_version} or %{fedora_version}
in any of the spec files i've looked at.

*shrug*

-greg