chore(image): pass all store paths at once via stdin to nix copy

flake.nix

@@ -163,11 +163,8 @@
             (finalizeScript
               # sh
               ''
-                while read entry; do
-                  [[ "$entry" == *.drv ]] && entry+="^*" || true
-                  nix copy --quiet --to "file://$(pwd)/.nix-cache" $entry || true
-                  echo -n "."
-                done
+                # add ^* to all store paths ending in .drv (prevent warning log spam)
+                ${pkgs.gnused}/bin/sed '/\.drv$/s/$/^*/' | nix copy --quiet --to "file://$(pwd)/.nix-cache" --stdin || true
               '')
           ];
           image-cachix = mkImage [