This is a very easy fix, to remove the following warning:
```
WARNING: Running the setup command as `meson [options]` instead of `meson setup [options]` is ambiguous and deprecated.
```
The fix is to just run `meson setup` instead and it works like a charm.
Related PRs: i3/i3lock#365 and i3/i3status#538.
The former two provide fallbacks in case $PAGER or $EDITOR is not set (which
might be more common than you think, because they have to be set in
~/.xsession, not in the shell configuration!) while the latter tries to launch
a terminal emulator. The scripts are most prominently used in i3-nagbar, which
alerts the user when the configuration is broken for some reason. Also,
i3-sensible-terminal is used in the default configuration.
This commit does not rely on the shell supporting ${PAGER:-less} anymore, which
is not the case for 'fish'.
