avahi: Move D-Bus conf file to share/dbus-1/system.d

Since D-Bus 1.9.18 configuration files installed by third-party should
go in share/dbus-1/system.d. The old location is for sysadmin overrides.

pkgs/development/libraries/avahi/default.nix

@@ -39,7 +39,7 @@ stdenv.mkDerivation rec {
 
   configureFlags =
     [ "--disable-qt3" "--disable-gdbm" "--disable-mono"
-      "--disable-gtk"
+      "--disable-gtk" "--with-dbus-sys=${placeholder "out"}/share/dbus-1/system.d"
       (stdenv.lib.enableFeature gtk3Support "gtk3")
       "--${if qt4Support then "enable" else "disable"}-qt4"
       (stdenv.lib.enableFeature withPython "python")