nixos/make-system-tarball: extra commands to be executed before archive

nixos/lib/make-system-tarball.sh

@@ -33,7 +33,7 @@ for i in $storePaths; do
 done
 
 
-# TODO tar ruxo 
+# TODO tar ruxo
 # Also include a manifest of the closures in a format suitable for
 # nix-store --load-db.
 printRegistration=1 perl $pathsFromGraph closure-* > nix-path-registration
@@ -48,6 +48,8 @@ for ((n = 0; n < ${#objects[*]}; n++)); do
     fi
 done
 
+$extraCommands
+
 mkdir -p $out/tarball
 
 tar cvJf $out/tarball/$fileName.tar.xz * $extraArgs