hopefully fix kernel panics making BSODs not visible under some circumstances?

src/lua/core/boot.lua

@@ -31,7 +31,11 @@ function boot.boot()
       gpu.setBackground(0x000000)
 
       native.sleep(4000000)
-      os.exit(1)
+      if modules.computer and modules.computer.shutdown() then
+        modules.computer.shutdown()
+      else
+        os.exit(1)
+      end
     end)
   end