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/cabin/default.nix

@@ -1,19 +1,21 @@
-{ stdenv, fetchzip }:
+{ lib, fetchFromGitHub }:
 
-fetchzip rec {
+fetchFromGitHub rec {
   name = "cabin-1.005";
 
-  url = https://github.com/impallari/Cabin/archive/982839c790e9dc57c343972aa34c51ed3b3677fd.zip;
+  owner = "impallari";
+  repo = "Cabin";
+  rev = "982839c790e9dc57c343972aa34c51ed3b3677fd";
 
   postFetch = ''
-    mkdir -p $out/share/{doc,fonts}
-    unzip -j $downloadedFile \*.otf                    -d $out/share/fonts/opentype
-    unzip -j $downloadedFile \*README.md \*FONTLOG.txt -d "$out/share/doc/${name}"
+    tar xf $downloadedFile --strip=1
+    install -m444 -Dt $out/share/fonts/opentype fonts/OTF/*.otf
+    install -m444 -Dt $out/share/doc/${name}    README.md FONTLOG.txt
   '';
 
-  sha256 = "1ax5c2iab48qsk9zn3gjvqaib2lnlm25f1wr0aysf5ngw0y0jkrd";
+  sha256 = "1bl7h217m695jn4rbniialfk573aa44fslp2rjxnhkicakpcm44h";
 
-  meta = with stdenv.lib; {
+  meta = with lib; {
     description = "A humanist sans with 4 weights and true italics";
     longDescription = ''
       The Cabin font family is a humanist sans with 4 weights and true italics,