Allow setting OS-level password

Bit ugly as it is, but we're slowly iterating towards a secret manager
I'm happy with.

os/rebuild.sh

@@ -39,7 +39,14 @@ then
 fi
 if [ "$verb" = "test" ] || [ "$verb" = "switch" ] || [ "$confirm" = "y" ]
 then
+  # Generate passwords first. If there's a missing one that cannot be generated, we'll know before anything is written
+  "$toplevel/bin/generate-passwords"
+  # Install the passwords to their respective directories
+  "$toplevel/bin/install-passwords"
   sudo nixos-rebuild --flake "$self#$HOSTNAME" test "${specialisationArgs[@]}" "$@"
+  # Fix passwords permission. After install, so it can use new users
+  "$toplevel/bin/fix-permissions-passwords"
+  # TODO Install passwords with correct permissions during activation
 fi
 
 # Set as boot