package/x11r7/xserver_xorg-server: Fix glamor dependency

X.org xserver depends on libepoxy for glamor support, which depends on
EGL support. Mesa3d is not the only possible EGL provider therefore
change the dependency check.

Signed-off-by: Bernd Kuhls <bernd.kuhls@t-online.de>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>