qtbase: Allow to build eglfs with x11 in DISTRO_FEATURES
* even when x11 is in DISTRO_FEATURES someone might configure qtbase
to build with eglfs, that works OK with Qt 5.5.1, because
-DEGL_API_FB=1 is also passed through
mkspecs/devices/linux-imx6-g++/qmake.conf
but with 5.6 and 5.7 it fails when X11 headers are include with their
own Status enum (the same errors like before
https://codereview.qt-project.org/#/c/105116/2)
Adding -DEGL_API_FB=1 like linux-imx6-g++/qmake.conf does is simplest
workaround to prevent imx-gpu-viv from including Xlib from
EGL/eglvivante.h
Signed-off-by: Martin Jansa <Martin.Jansa@gmail.com> Signed-off-by: Otavio Salvador <otavio@ossystems.com.br>
