update nvidia detection to handle hosts that use runtime with no GPU

Author: thelamer

root/defaults/startwm.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/with-contenv bash
 
 # Enable Nvidia GPU support if detected
-if which nvidia-smi; then
+if which nvidia-smi > /dev/null 2>&1 && ls -A /dev/dri 2>/dev/null && [ "${DISABLE_ZINK}" == "false" ]; then
   export LIBGL_KOPPER_DRI2=1
   export MESA_LOADER_DRIVER_OVERRIDE=zink
   export GALLIUM_DRIVER=zink