Use common gemrc in posix substrates
Use common gemrc in posix substrates

mitchellh/vagrant-installers,chrisroberts/vagrant-installers,chrisroberts/vagrant-installers,chrisroberts/vagrant-installers,chrisroberts/vagrant-installers,mitchellh/vagrant-installers,mitchellh/vagrant-installers,mitchellh/vagrant-installers,mitchellh/vagrant-installers,mitchellh/vagrant-installers,chrisroberts/vagrant-installers,chrisroberts/vagrant-installers