Adding onto this, as I mentioned an additional step, I can also imagine
defining some macros which would be used in the .spec file. We could
have a simple generic one that would be available within rpm with the
extension possibility of each working group defining their own macros
which they would use in their own ecosystems.
Debian has an article about reproducible packaging:
https://wiki.debian.org/ReproducibleBuilds/Howto#Introduction
Especially look for the string: "tarball"
--
Marián Konček