vagrant-vbguest-create-symlink

class MyInstaller < VagrantVbguest::Installers::Linux
  def install(opts=nil, &block)
	super
	communicate.sudo('ln -s /opt/VBoxGuestAdditions-*/lib/VBoxGuestAdditions /usr/lib', opts, &block)
  end
end

Vagrant.configure("2") do |config|
  config.vbguest.installer = MyInstaller
  ...
end