xfree86: Create a symlink X -> Xorg when installing using meson

This brings the behavior closer than what we currently have with
autotools-based build system.

Meson does not currently have native support for symlinks.
See https://github.com/mesonbuild/meson/issues/1602.

Signed-off-by: Povilas Kanapickas <povilas@radix.lt>
4 jobs for meson-xorg-x-symlink in 5 minutes and 30 seconds (queued for 1 second)
Status Job ID Name Coverage
  Docker Image
passed #8326457
debian-buster

00:00:21

 
  Build And Test
passed #8326458
autotools

00:05:09

passed #8326459
meson

00:01:28

passed #8326460
meson-noglamor

00:01:37