zd1211-firmware: less fixed-output derivation

Move some logic out of the fixed-output fetchzip and to a
'regular' derivation

pkgs/os-specific/linux/firmware/zd1211/default.nix

···
-{ lib, fetchzip }:
+{ stdenv
+, lib
+, fetchurl
+}:
 
-let
+stdenv.mkDerivation rec {
   pname = "zd1211-firmware";
   version = "1.5";
-in fetchzip rec {
-  name = "${pname}-${version}";
-  url = "mirror://sourceforge/zd1211/${name}.tar.bz2";
 
-  postFetch = ''
-    tar -xjvf $downloadedFile
+  src = fetchurl {
+    url = "mirror://sourceforge/zd1211/${pname}-${version}.tar.bz2";
+    hash = "sha256-8R04ENf3KDOZf2NFhKWG3M7XGjU/llq/gQYuxDHQKxI=";
+  };
+
+  installPhase = ''
+    runHook preInstall
+
     mkdir -p $out/lib/firmware/zd1211
-    cp zd1211-firmware/* $out/lib/firmware/zd1211
-  '';
+    cp * $out/lib/firmware/zd1211
 
-  sha256 = "0sj2zl3r0549mjz37xy6iilm1hm7ak5ax02gwrn81r5yvphqzd52";
+    runHook postInstall
+  '';
 
   meta = {
     description = "Firmware for the ZyDAS ZD1211(b) 802.11a/b/g USB WLAN chip";