Do you observe the same problem with tar 1.27? What user-ID is the build user? I.e., what's the output of the 'id' command, or its equivalent on your system? (Or, if the files are owned by someone else, what's the output of 'ls -ln' for those files?)
If the builder's ID is indeed greater than 2097151 that will break tests of old tar format, and we should probably adjust the tests to not worry about that. Old tar format can't represent such IDs.
