xorg-server: Force -Dglamor=true

With the DDX drivers gone, we must use Glamor to provide the modeset
driver or X server won't start.

x/installing/xorg-server.xml

@@ -120,7 +120,7 @@ cd    build &&
 meson setup ..              \
       --prefix=$XORG_PREFIX \
       --localstatedir=/var  \
-      -Dsuid_wrapper=true   \
+      -Dglamor=true         \
       -Dxkb_output_dir=/var/lib/xkb &&
 ninja</userinput></screen>
 
@@ -152,8 +152,14 @@ mkdir -pv /etc/X11/xorg.conf.d</userinput></screen>
     <title>Command Explanations</title>
 
     <para>
-      <parameter>-Dsuid_wrapper=true</parameter>: Builds the suid-root
-      wrapper for legacy driver support on rootless xserver systems.
+      <parameter>-Dglamor=true</parameter>: Ensure building the Glamor
+      module.  It's needed to run the Xorg server without Device Dependant X
+      (DDX) drivers.
+    </para>
+
+    <para>
+      <option>-Dsuid_wrapper=true</option>: Builds the suid-root
+      wrapper for legacy DDX driver support on rootless xserver systems.
     </para>
 
     <para>