opensans-ttf: make the font derivations fixed-output (#28126)

- [x] dead link fixed
- [x] make the font derivations fixed-output (https://github.com/NixOS/nixpkgs/issues/27754)

pkgs/data/fonts/opensans-ttf/default.nix

@@ -1,22 +1,18 @@
-{stdenv, fetchurl}:
+{stdenv, fetchzip}:
 
-# adapted from https://aur.archlinux.org/packages/tt/ttf-opensans/PKGBUILD
-
-stdenv.mkDerivation rec {
+fetchzip {
   name = "opensans-ttf-20140617";
 
-  src = fetchurl {
-    url = "https://hexchain.org/pub/archlinux/ttf-opensans/opensans.tar.gz";
-    sha256 = "1ycn39dijhd3lffmafminrnfmymdig2jvc6i47bb42fx777q97q4";
-  };
+  url = "http://web.archive.org/web/20150801161609/https://hexchain.org/pub/archlinux/ttf-opensans/opensans.tar.gz";
 
-  sourceRoot = ".";
-
-  installPhase = ''
+  postFetch = ''
+    tar -xzf $downloadedFile
     mkdir -p $out/share/fonts/truetype
     cp *.ttf $out/share/fonts/truetype
   '';
 
+  sha256 = "0zpzqw5y9g5jk7xjcxa12ds60ckvxmpw8p7bnkkmad53s94yr5wf";
+
   meta = {
     description = "Open Sans fonts";
     longDescription = ''