data/fonts: cleanup

* make font derivations fixed-output where applicable
 * fix dead links
 * `stdenv.lib` -> `lib` where `stdenv` is not involved
 * remove `meta.platforms = [ unix ]` and `meta.platforms = [ linux ]` because the restriction has no sense for data packages

pkgs/data/fonts/lalezar-fonts/default.nix

@@ -1,22 +1,22 @@
-{ stdenv, fetchFromGitHub }:
+{ lib, fetchFromGitHub }:
 
-stdenv.mkDerivation rec {
+let
   pname = "lalezar-fonts";
   version = "unstable-2017-02-28";
+in fetchFromGitHub {
+  name = "${pname}-${version}";
+  owner = "BornaIz";
+  repo = "Lalezar";
+  rev = "238701c4241f207e92515f845a199be9131c1109";
 
-  src = fetchFromGitHub {
-    owner = "BornaIz";
-    repo = "Lalezar";
-    rev = "238701c4241f207e92515f845a199be9131c1109";
-    sha256 = "1j3zg9qw4ahw52i0i2c69gv5gjc1f4zsdla58kd9visk03qgk77p";
-  };
-
-  installPhase = ''
+  postFetch = ''
+    tar xf $downloadedFile --strip=1
     mkdir -p $out/share/fonts/lalezar-fonts
     cp -v $( find . -name '*.ttf') $out/share/fonts/lalezar-fonts
   '';
+  sha256 = "0jmwhr2dqgj3vn0v26jh6c0id6n3wd6as3bq39xa870zlk7v307b";
 
-  meta = with stdenv.lib; {
+  meta = with lib; {
     homepage = https://github.com/BornaIz/Lalezar;
     description = "A multi-script display typeface for popular culture";
     license = licenses.ofl;