vagrant: Use dummy file for the console output

Links:
- https://bugs.launchpad.net/cloud-images/+bug/1874453

live-build/ubuntu-cpc/hooks.d/base/vagrant.binary

@@ -156,6 +156,8 @@ Vagrant.configure("2") do |config|
      vb.customize [ "modifyvm", :id, "--uart1", "0x3F8", "4" ]
      # Creating a console log file is not an expected behavior for vagrant boxes. LP #1777827
      #vb.customize [ "modifyvm", :id, "--uartmode1", "file", File.join(Dir.pwd, "${prefix}-console.log") ]
+     # Use dummy file for the console output. LP #1874453
+     vb.customize [ "modifyvm", :id, "--uartmode1", "file", File::NULL ]
   end
 end
 EOF