tarsnap: fix build on darwin aarch64/arm64

pkgs/tools/backup/tarsnap/default.nix

@@ -1,4 +1,4 @@
-{ lib, stdenv, fetchurl, openssl, zlib, e2fsprogs, bash }:
+{ lib, stdenv, fetchurl, openssl, zlib, e2fsprogs, bash, bzip2 }:
 
 let
   zshCompletion = fetchurl {
@@ -31,7 +31,8 @@ stdenv.mkDerivation rec {
     install -m 444 -D ${zshCompletion} $out/share/zsh/site-functions/_tarsnap
   '';
 
-  buildInputs = [ openssl zlib ] ++ lib.optional stdenv.isLinux e2fsprogs ;
+  buildInputs = [ openssl zlib ] ++ lib.optional stdenv.isLinux e2fsprogs
+                ++ lib.optional stdenv.isDarwin bzip2;
 
   meta = {
     description = "Online backups for the truly paranoid";