Add setup-hook to hicolor_icon_theme

pkgs/data/icons/hicolor-icon-theme/default.nix

@@ -8,6 +8,8 @@ stdenv.mkDerivation rec {
     sha256 = "01ilkizzal3wq2naaj84rqmd850aari1ahiw9vfis3a82n4h72x3";
   };
 
+  setupHook = ./setup-hook.sh;
+
   meta = {
     description = "Default fallback theme used by implementations of the icon theme specification";
     homepage = http://icon-theme.freedesktop.org/releases/;

pkgs/data/icons/hicolor-icon-theme/setup-hook.sh

@@ -0,0 +1,20 @@
+# Populate XDG_ICON_DIRS
+hicolorIconThemeHook() {
+
+    # where to find icon themes
+    if [ -d "$1/share/icons" ]; then
+      addToSearchPath XDG_ICON_DIRS $1/share
+    fi
+	
+}
+
+envHooks+=(hicolorIconThemeHook)
+
+# Remove icon cache
+hicolorPreFixupPhase() {
+    rm -f $out/share/icons/hicolor/icon-theme.cache
+    rm -f $out/share/icons/HighContrast/icon-theme.cache
+}
+
+preFixupPhases="$preFixupPhases hicolorPreFixupPhase"
+