meson: use install_emptydir() and drop meson-make-symlink.sh

The script is mostly equivalent to 'mkdir -p' and 'ln -sfr'.
Let's replace it with install_emptydir() builtin function and
inline meson call.

network/meson.build

@@ -14,8 +14,7 @@ if conf.get('ENABLE_NETWORKD') == 1
                      install_dir : networkdir)
 
         if install_sysconfdir
-                meson.add_install_script('sh', '-c',
-                                         mkdir_p.format(sysconfdir / 'systemd/network'))
+                install_emptydir(sysconfdir / 'systemd/network')
         endif
 endif