mkBinaryCache: support different compression methods: xz (default), zstd, none

nixos/tests/binary-cache.nix

@@ -1,8 +1,10 @@
+{ compression, ... }@args:
+
 import ./make-test-python.nix (
   { lib, pkgs, ... }:
 
   {
-    name = "binary-cache";
+    name = "binary-cache-" + compression;
     meta.maintainers = with lib.maintainers; [ thomasjm ];
 
     nodes.machine =
@@ -24,7 +26,12 @@ import ./make-test-python.nix (
               nativeBuildInputs = [ openssl ];
             }
             ''
-              tar -czf tmp.tar.gz -C "${mkBinaryCache { rootPaths = [ hello ]; }}" .
+              tar -czf tmp.tar.gz -C "${
+                mkBinaryCache {
+                  rootPaths = [ hello ];
+                  inherit compression;
+                }
+              }" .
               openssl enc -aes-256-cbc -salt -in tmp.tar.gz -out $out -k mysecretpassword
             '';
 
@@ -78,4 +85,4 @@ import ./make-test-python.nix (
       machine.succeed("[ -d %s ] || exit 1" % storePath)
     '';
   }
-)
+) args