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/open-sans/default.nix

@@ -1,25 +1,23 @@
-{ stdenv, fetchFromGitLab }:
+{ lib, fetchFromGitLab }:
 
-stdenv.mkDerivation rec {
+let
   pname = "open-sans";
   version = "1.11";
+in fetchFromGitLab rec {
+  name = "${pname}-${version}";
 
-  src = fetchFromGitLab {
-    domain = "salsa.debian.org";
-    owner = "fonts-team";
-    repo = "fonts-open-sans";
-    rev = "debian%2F1.11-1"; # URL-encoded form of "debian/1.11-1" tag
-    sha256 = "077hkvpmk3ghbqyb901w43b2m2a27lh8ddasyx1x7pdwyr2bjjl2";
-  };
-
-  dontBuild = true;
-
-  installPhase = ''
+  domain = "salsa.debian.org";
+  owner = "fonts-team";
+  repo = "fonts-open-sans";
+  rev = "debian%2F1.11-1"; # URL-encoded form of "debian/1.11-1" tag
+  postFetch = ''
+    tar xf $downloadedFile --strip=1
     mkdir -p $out/share/fonts/truetype
     cp *.ttf $out/share/fonts/truetype
   '';
+  sha256 = "146ginwx18z624z582lrnhil8jvi9bjg6843265bgxxrfmf75vhp";
 
-  meta = with stdenv.lib; {
+  meta = with lib; {
     description = "Open Sans fonts";
     longDescription = ''
       Open Sans is a humanist sans serif typeface designed by Steve Matteson,