fix non-update build-script if package installed with no-url (skip build)

assets/var/gnu/unitprint/backend-local/s6.md

@@ -1,11 +1,15 @@
-unitprint/backend-local/s6
+<pkgname>/s6
 =
 
 
 ``` sh *** set ***
-ln -sf $(pwd) /pkg/gnu/s6/etc/service/current/unitprint-backend-local
+pkgname_flat=${pkgname//\//\~}
+pkgname_flat=${pkgname_flat%\~s6}
+ln -sf $(pwd) /pkg/gnu/s6/etc/service/current/$pkgname_flat
+s6-svscanctl -h /pkg/gnu/s6/etc/service/current
 ```
 
 ``` sh *** off ***
-rm /pkg/gnu/s6/etc/service/current/unitprint-backend-local
+pkgname_flat=${pkgname//\//\~}
+rm /pkg/gnu/s6/etc/service/current/$pkgname_flat
 ```