Match the modern desktop expectation set by systemd [0] and relied on by some
software (GNOME/glib, icecat, ungoogle-chromium, etc.).
[0] https://www.man7.org/linux/man-pages/man5/localtime.5.html
* gnu/tests/base.scm
("/etc/localtime is a symlink to the timezone data file"): New test.
Change-Id: I8fb95abb6a3e455dd7019d5d798f7862d16b6263
Reviewed-by: Ludovic Courtès <ludo@gnu.org>