awesome: Allows awesome to load svg images.

Awesome can load SVG images, just like it can do PNG, through gdk.

The support for SVG images through GDK needs librvsg.

This commits adds the plumbing necessary in the wrapper that makes
awesome be able to load SVG images.

Without this, awesome will not load SVG images. The related error message is:

 > Couldn't recognize the image file format for file

Which comes from gdk.

pkgs/applications/window-managers/awesome/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, fetchFromGitHub, luaPackages, cairo, cmake, imagemagick, pkgconfig, gdk_pixbuf
+{ stdenv, fetchurl, fetchFromGitHub, luaPackages, cairo, librsvg, cmake, imagemagick, pkgconfig, gdk_pixbuf
 , xorg, libstartup_notification, libxdg_basedir, libpthreadstubs
 , xcb-util-cursor, makeWrapper, pango, gobjectIntrospection, unclutter
 , compton, procps, iproute, coreutils, curl, alsaUtils, findutils, xterm
@@ -30,7 +30,7 @@ with luaPackages; stdenv.mkDerivation rec {
   ];
 
   propagatedUserEnvPkgs = [ hicolor_icon_theme ];
-  buildInputs = [ cairo dbus gdk_pixbuf gobjectIntrospection
+  buildInputs = [ cairo librsvg dbus gdk_pixbuf gobjectIntrospection
                   git lgi libpthreadstubs libstartup_notification
                   libxdg_basedir lua nettools pango xcb-util-cursor
                   xorg.libXau xorg.libXdmcp xorg.libxcb xorg.libxshmfence
@@ -54,6 +54,7 @@ with luaPackages; stdenv.mkDerivation rec {
 
   postInstall = ''
     wrapProgram $out/bin/awesome \
+      --set GDK_PIXBUF_MODULE_FILE "$GDK_PIXBUF_MODULE_FILE" \
       --prefix LUA_CPATH ";" '"${lgi}/lib/lua/${lua.luaversion}/?.so"' \
       --prefix LUA_PATH ";" '"${lgi}/share/lua/${lua.luaversion}/?.lua;${lgi}/share/lua/${lua.luaversion}/lgi/?.lua"' \
       --prefix GI_TYPELIB_PATH : "$GI_TYPELIB_PATH" \