dockerTools: rsync contents with -keep-dirlinks

pkgs/build-support/docker/default.nix

@@ -247,7 +247,7 @@ rec {
         echo "Adding contents..."
         for item in $contents; do
           echo "Adding $item"
-          rsync -a $item/ layer/
+          rsync -ak $item/ layer/
         done
       else
         echo "No contents to add to layer."
@@ -310,7 +310,7 @@ rec {
         echo "Adding contents..."
         for item in ${toString contents}; do
           echo "Adding $item..."
-          rsync -a $item/ layer/
+          rsync -ak $item/ layer/
         done
       '';