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/manrope/default.nix

@@ -1,19 +1,19 @@
-{ stdenv, fetchFromGitHub }:
+{ lib, fetchFromGitHub }:
 
-stdenv.mkDerivation rec {
+let
   pname = "manrope";
   version = "3";
-  src = fetchFromGitHub {
-    owner = "sharanda";
-    repo = pname;
-    rev = "3bd68c0c325861e32704470a90dfc1868a5c37e9";
-    sha256 = "1k6nmczbl97b9j2a8vx6a1r3q4gd1c2qydv0y9gn8xyl7x8fcvhs";
-  };
-  dontBuild = true;
-  installPhase = ''
+in fetchFromGitHub {
+  name = "${pname}-${version}";
+  owner = "sharanda";
+  repo = pname;
+  rev = "3bd68c0c325861e32704470a90dfc1868a5c37e9";
+  sha256 = "1h4chkfbp75hrrqqarf28ld4yb7hfrr7q4w5yz96ivg94lbwlnld";
+  postFetch = ''
+    tar xf $downloadedFile --strip=1
     install -Dm644 -t $out/share/fonts/opentype "desktop font"/*
   '';
-  meta = with stdenv.lib; {
+  meta = with lib; {
     description = "Open-source modern sans-serif font family";
     homepage = https://github.com/sharanda/manrope;
     license = licenses.ofl;