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/vegur/default.nix

@@ -1,29 +1,22 @@
-{ stdenv, rpmextract, fetchurl, unzip }:
+{ lib, buildPackages, fetchzip }:
 
-stdenv.mkDerivation rec {
+let
   version = "0.701";
+in fetchzip {
   name = "vegur-font-${version}";
 
   # Upstream doesn't version their URLs.
   # http://dotcolon.net/font/vegur/ → http://dotcolon.net/DL/font/vegur.zip
-  src = fetchurl {
-    url = "http://download.opensuse.org/repositories/M17N:/fonts/SLE_12_SP3/src/dotcolon-vegur-fonts-0.701-1.4.src.rpm";
-    sha256 = "0ra3fds3b352rpzn0015km539c3l2ik2lqd5x6fr65ss9fg2xn34";
-  };
+  url = "http://download.opensuse.org/repositories/M17N:/fonts/SLE_12_SP3/src/dotcolon-vegur-fonts-0.701-1.4.src.rpm";
 
-  nativeBuildInputs = [ rpmextract unzip ];
-
-  unpackPhase = ''
-    rpmextract $src
+  postFetch = ''
+    ${buildPackages.rpmextract}/bin/rpmextract $downloadedFile
     unzip vegur.zip
+    install -m444 -Dt $out/share/fonts/Vegur *.otf
   '';
+  sha256 = "0iisi2scq72lyj7pc1f36fhfjnm676n5byl4zaavhbxpdrbc6d1v";
 
-  installPhase = ''
-    mkdir -p $out/share/fonts/Vegur
-    cp *.otf $out/share/fonts/Vegur
-  '';
-
-  meta = with stdenv.lib; {
+  meta = with lib; {
     homepage = http://dotcolon.net/font/vegur/;
     description = "A humanist sans serif font.";
     platforms = platforms.all;