The "builds" file used to be part of the Tclkit 8.4.1, now superceded with newer versions.
You can still find an old copy of that file at:
https://www.equi4.com/pub/tk/8.4.1/builds.html
More information and details about the latest builds are on the Tclkit homepage:
https://www.equi4.com/tclkit