creating an SPN from a linux build server

When you use the setspn tool, all you're doing is modifying the servicePrincipalName attribute of the specified computer/user in AD.

To do the same from a Linux machine, you just need to use an LDAP tool to connect to a domain controller and modify the attribute like you would any other. Keep in mind that it's a multi-valued attribute though. So don't accidentally wipe out existing entries that might exist on the target.