editors: Prevent ctags from following symlinks

editors: Prevent ctags from following symlinks

Some tests will create a subtree of /sys under build/test/sys and
depending on the local system that tree might end up having an infinite
chain of symlinks. For example:

  $ ls build/test/sys/devices/pnp0/00:00/subsystem/devices/00:00/subsystem/devices/00:00/subsystem/devices/00:00/subsystem/devices/00:00/subsystem/devices/00:00/subsystem/
  devices  drivers  drivers_autoprobe

Exuberant ctags will by default follow symlinks, so configure it not to
do so through a local .ctags file setting --links=no.

Tested that `ctags -R` doesn't get stuck with the dotfile present.