Please make the build reproducibility independent from the timezone

The Debian reproducible builds effort tells me that tor is not reproducible when the timezone varies: https://tests.reproducible-builds.org/debian/rb-pkg/unstable/amd64/tor.html

The "reproducible" branch in the https://git-tails.immerda.ch/tor repository fixes that for me (tested on top of the tor-0.2.8.4-rc-1 package).

It would be nice to have this tiny fix in 0.2.8 final :)