fixup ext2 image generation

nixos-modules/lib/make-ext2-fs.nix

@@ -4,7 +4,7 @@ let
   grub' = pkgs.buildPackages.grub2_efi;
 
   copyEris = lib.strings.concatMapStrings ({ source, target }: ''
-    cp -a --reflink=auto -t "./rootImage/${target}" "${source}"
+    cp -a --reflink=auto "${source}" "./rootImage/${target}"
   '') contents;
 
 in pkgs.stdenv.mkDerivation {
@@ -50,6 +50,7 @@ in pkgs.stdenv.mkDerivation {
       done
     )
 
+    mkdir ./rootImage/eris
     ${copyEris}
 
     # Make a crude approximation of the size of the target image.