Thsi fixed a regression in 8f75c2e279

The bundler script doesn't do anything (it literally exits right at the top)
when skipping the bundle. This is arguably wrong, because it doesn't generate
"ip.txt", the file with the bundler IP address either!

So, generate that ourselves. While ding this, also drop the need for xip.io,
which has also been removed from RN, since it gives more trouble than it solves.