distro: speed up guix lookup (#1452)

neofetch

@@ -1031,7 +1031,7 @@ get_distro() {
             elif type -p guix >/dev/null; then
                 case $distro_shorthand in
                     on|tiny) distro="Guix System" ;;
-                    *) distro="Guix System $(guix system -V | awk 'NR==1{printf $5}')"
+                    *) distro="Guix System $(guix -V | awk 'NR==1{printf $4}')"
                 esac
 
             # Display whether using '-current' or '-release' on OpenBSD.