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/hasklig/default.nix

@@ -1,4 +1,4 @@
-{stdenv, fetchzip}:
+{ lib, fetchzip }:
 
 let
   version = "1.1";
@@ -9,13 +9,12 @@ in fetchzip {
 
   postFetch = ''
     unzip $downloadedFile
-    mkdir -p $out/share/fonts/opentype
-    cp *.otf $out/share/fonts/opentype
+    install -m444 -Dt $out/share/fonts/opentype *.otf
   '';
 
   sha256 = "0xxyx0nkapviqaqmf3b610nq17k20afirvc72l32pfspsbxz8ybq";
 
-  meta = with stdenv.lib; {
+  meta = with lib; {
     homepage = https://github.com/i-tu/Hasklig;
     description = "A font with ligatures for Haskell code based off Source Code Pro";
     license = licenses.ofl;