make-iso9660-image: drop references to build closure

Changed files
+4
nixos
+4
nixos/lib/make-iso9660-image.nix
···
name = isoName;
__structuredAttrs = true;
+
# the image will be self-contained so we can drop references
+
# to the closure that was used to build it
+
unsafeDiscardReferences.out = true;
+
buildCommandPath = ./make-iso9660-image.sh;
nativeBuildInputs = [
xorriso