Adding git origin url to be used with relative submodule path

The qt5 repository was fetched without remote url, which prevents
using releative submodule spec in .gitmodules with early 1.7.x git
versions.

Change-Id: I43d5e321756e11c65ce63a80a6f1fb21a70d5d79
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@digia.com>