xfree86: meson: Use install_symlink function instead of a hack.

This was a old hack used before Meson 0.61.0 added install_symlink, we
are at the meson release 1.10.0 so it is safe to use the new proper
function for this task.

Also used the X server's executable name as the link target name, and as
the SUID wrapper's name.

Moved the minimum Meson version up to 0.61.0.

Signed-off-by: b-aaz <b-aazbsd@proton.me>

meson.build

@@ -4,7 +4,7 @@ project('xserver', 'c',
             'c_std=gnu99',
         ],
         version: '25.0.0.7',
-        meson_version: '>= 0.58.0',
+        meson_version: '>= 0.61.0',
 )
 release_date = '2025-07-29'