make-system-tarball: use `pixz -t`

Pass `-t` to pixz to prevent it from appending an index to the end of
the uncompressed stream, confusing tools such as `machinectl import-tar`.

Fixes: #187816

Changed files
+1 -1
nixos
+1 -1
nixos/lib/make-system-tarball.nix
···
# Extra tar arguments
, extraArgs ? ""
# Command used for compression
-
, compressCommand ? "pixz"
+
, compressCommand ? "pixz -t"
# Extension for the compressed tarball
, compressionExtension ? ".xz"
# extra inputs, like the compressor to use