Using Nix[0] should solve the reproducibility of a package. We use its package manager for bob[1] to achieve reproducible builds for projects.
If a `make install` invocation gzips manpages instead of the package manager or distro hooks, then you won't have reproducible manpages unless the upstream uses the `-n` switch as well. This is just an example of many small and obscure issues that hide inn different upstream projects.