linuxPackages.nvidia_x11_beta: fix optix denoiser

OptiX tries loading `$ORIGIN/nvoptix.bin` before
`/usr/share/nvidia/nvoptix.bin`.

Additionally OptiX isn't supported for 32-bit.

pkgs/os-specific/linux/nvidia-x11/builder.sh

@@ -126,6 +126,12 @@ installPhase() {
         fi
     done
 
+
+    # OptiX tries loading `$ORIGIN/nvoptix.bin` first
+    if [ -e nvoptix.bin ]; then
+        install -Dm444 -t $out/lib/ nvoptix.bin
+    fi
+
     if [ -n "$bin" ]; then
         # Install the X drivers.
         mkdir -p $bin/lib/xorg/modules