package/nvidia-driver: Add gl.pc

In order to compile xserver, libgl provider have to provide gl.pc file.

Signed-off-by: Jérôme Pouiller <jezz@sysmic.org>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>