qt5base: fix build when egl headers need a definition

The build with gpu-viv-bin-mx6q libraries was broken since it wasn't
using "-DEGL_API_FB=1" flag which is found in egl.pc.

Signed-off-by: Fatih Aşıcı <fatih.asici@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>