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/go-font/default.nix

@@ -1,26 +1,22 @@
 { stdenv, fetchgit }:
 
-stdenv.mkDerivation rec {
-  name = "go-font-${version}";
+let
   version = "2017-03-30";
+in (fetchgit {
+  name = "go-font-${version}";
+  url = "https://go.googlesource.com/image";
+  rev = "f03a046406d4d7fbfd4ed29f554da8f6114049fc";
 
-  src = fetchgit {
-    url = "https://go.googlesource.com/image";
-    rev = "f03a046406d4d7fbfd4ed29f554da8f6114049fc";
-    sha256 = "1aq6mnjayks55gd9ahavk6jfydlq5lm4xm0xk4pd5sqa74p5p74d";
-  };
-
-  installPhase = ''
+  postFetch = ''
+    mv $out/* .
     mkdir -p $out/share/fonts/truetype
     mkdir -p $out/share/doc/go-font
     cp font/gofont/ttfs/* $out/share/fonts/truetype
     mv $out/share/fonts/truetype/README $out/share/doc/go-font/LICENSE
   '';
 
-  outputHashAlgo = "sha256";
-  outputHashMode = "recursive";
-  outputHash = "10hfm2cpxlx1ng7r2mbvykjhmy131qlgzpdzj7ibg9kr293bcjc0";
-
+  sha256 = "1488426ya2nzmwjas947fx9h5wzxrp9wasn8nkjqf0y0mpd4f1xz";
+}) // {
   meta = with stdenv.lib; {
     homepage = https://blog.golang.org/go-fonts;
     description = "The Go font family";