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/fixedsys-excelsior/default.nix

@@ -1,33 +1,25 @@
 { stdenv, fetchurl } :
 
-let 
+let
   major = "3";
   minor = "00";
   version = "${major}.${minor}";
-
-in
-
-stdenv.mkDerivation rec {
+in fetchurl rec {
   name = "fixedsys-excelsior-${version}";
 
-  src = fetchurl {
-    url = http://www.fixedsysexcelsior.com/fonts/FSEX300.ttf;
-    sha256 = "6ee0f3573bc5e33e93b616ef6282f49bc0e227a31aa753ac76ed2e3f3d02056d";
-  };
-
-  phases = [ "installPhase" ];
-
-  installPhase = ''
-    mkdir -p $out/share/fonts/truetype/
-    cp $src $out/share/fonts/truetype/${name}.ttf
+  urls = [
+    http://www.fixedsysexcelsior.com/fonts/FSEX300.ttf
+    https://raw.githubusercontent.com/chrissimpkins/codeface/master/fonts/fixed-sys-excelsior/FSEX300.ttf
+    http://tarballs.nixos.org/sha256/6ee0f3573bc5e33e93b616ef6282f49bc0e227a31aa753ac76ed2e3f3d02056d
+  ];
+  downloadToTemp = true;
+  recursiveHash = true;
+  postFetch = ''
+    install -m444 -D $downloadedFile $out/share/fonts/truetype/${name}.ttf
   '';
 
-  outputHashMode = "recursive";
+  sha256 = "32d6f07f1ff08c764357f8478892b2ba5ade23427af99759f34a0ba24bcd2e37";
 
-  outputHashAlgo = "sha256";
-
-  outputHash = "32d6f07f1ff08c764357f8478892b2ba5ade23427af99759f34a0ba24bcd2e37";
-  
   meta = {
     description = "Pan-unicode version of Fixedsys, a classic DOS font.";
     homepage = http://www.fixedsysexcelsior.com/;