Add qt.520.gcc_64.essentials files back

These files were removed by mistake, so bringing them back again.

This amends 6aeb8b93e5827682c7f3e89b70ba931092e3b877

Change-Id: I9ac55734f90ac4d2038531803253c61afa483647
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>