faba-mono-icons: build GTK icon cache

pkgs/data/icons/faba-mono-icons/default.nix

···
-{ stdenv, fetchFromGitHub, autoreconfHook, moka-icon-theme  }:
+{ stdenv, fetchFromGitHub, autoreconfHook, gtk3, moka-icon-theme }:
 
 stdenv.mkDerivation rec {
-  name = "${package-name}-${version}";
-  package-name = "faba-mono-icons";
+  name = "${pname}-${version}";
+  pname = "faba-mono-icons";
   version = "2016-04-30";
 
   src = fetchFromGitHub {
     owner = "snwh";
-    repo = package-name;
+    repo = pname;
     rev = "2006c5281eb988c799068734f289a85443800cda";
     sha256 = "0nisfl92y6hrbakp9qxi0ygayl6avkzrhwirg6854bwqjy2dvjv9";
   };
 
-  nativeBuildInputs = [ autoreconfHook ];
+  nativeBuildInputs = [ autoreconfHook gtk3 moka-icon-theme ];
 
-  buildInputs = [ moka-icon-theme ];
+  postFixup = ''
+    for theme in $out/share/icons/*; do
+      gtk-update-icon-cache $theme
+    done
+  '';
 
   meta = with stdenv.lib; {
     description = "The full set of Faba monochrome panel icons";
     homepage = https://snwh.org/moka;
-    license = with licenses; [ gpl3 ];
+    license = licenses.gpl3;
     platforms = platforms.all;
     maintainers = with maintainers; [ romildo ];
   };