This was always in the lock file and we can simply actually print it.
The test for this is a little bit silly but it should correctly
control for my daring to exercise timezone code *and* locale code in a
test, which I strongly suspect nobody dared do before.
Sample (abridged):
```
Path: /nix/store/gaxb42z68bcr8lch467shvmnhjjzgd8b-source
Last modified: 1970-01-01 00:16:40
Inputs:
├───flake-compat: github:edolstra/flake-compat/0f9255e01c2351cc7d116c072cb317785dd33b33
│ Last modified: 2023-10-04 13:37:54
├───flake-utils: github:numtide/flake-utils/b1d9ab70662946ef0850d488da1c9019f3a9752a
│ Last modified: 2024-03-11 08:33:50
│ └───systems: github:nix-systems/default/da67096a3b9bf56a91d16901293e51ba5b49a27e
│ Last modified: 2023-04-09 08:27:08
```
Change-Id: I355f82cb4b633974295375ebad646fb6e2107f9b
bd1344ec54