In preparation for the Wayland backend, this patch enables the EGL context creation option for X11 as a replacement for GLX. The EGL context creation is activated on build time via:
make lite debug ninja BUILD_DIR=~/Development/blender_build_x11_egl BUILD_CMAKE_ARGS="-DWITH_GL_EGL=ON"
Previously, this would not build due to the use of GLX related functions. This patch enables the EGL context as option.