cinnamon.mint-y-icons: add missing parent icon themes

Also:
- add runHook calls
- move postFixup actions to installPhase
- gtk-update-icon-cache does accepts only one icon path

pkgs/desktops/cinnamon/mint-y-icons/default.nix

@@ -1,6 +1,7 @@
 { fetchFromGitHub
 , stdenv
 , gnome3
+, gnome-icon-theme
 , hicolor-icon-theme
 , gtk3
 }:
@@ -16,8 +17,9 @@ stdenv.mkDerivation rec {
     sha256 = "1c2a79ylk363i982czwwqcwc7cw6dyzlqphcypqm6nll7xlafq8s";
   };
 
-  propagatedUserEnvPkgs = [
+  propagatedBuildInputs = [
     gnome3.adwaita-icon-theme
+    gnome-icon-theme
     hicolor-icon-theme
   ];
 
@@ -25,15 +27,19 @@ stdenv.mkDerivation rec {
     gtk3
   ];
 
-  postFixup =  ''
-    gtk-update-icon-cache $out/share/icons/*
-  '';
-
   dontDropIconThemeCache = true;
 
   installPhase = ''
+    runHook preInstall
+
     mkdir -p $out
     mv usr/share $out
+
+    for theme in $out/share/icons/*; do
+      gtk-update-icon-cache $theme
+    done
+
+    runHook postInstall
   '';
 
   meta = with stdenv.lib; {