Make /var/lib/nginx optional

So it's easier to reuse this in distros like Ubuntu

Signed-off-by: Tommy <contact@tommytran.io>

etc/systemd/system/nginx.service.d/override.conf

@@ -18,7 +18,7 @@ ProtectKernelModules=true
 ProtectKernelTunables=true
 ProtectProc=invisible
 ProtectSystem=strict
-ReadWritePaths=/var/lib/nginx /var/log/nginx -/var/cache/nginx
+ReadWritePaths=-/var/lib/nginx /var/log/nginx -/var/cache/nginx
 RestrictAddressFamilies=AF_INET AF_INET6 AF_UNIX
 RestrictNamespaces=true
 RestrictRealtime=true
@@ -27,4 +27,4 @@ RuntimeDirectory=nginx
 RuntimeDirectoryMode=700
 SystemCallArchitectures=native
 SystemCallFilter=@system-service
-SystemCallFilter=~@obsolete
+SystemCallFilter=~@obsolete