Can the Macbook 12 inch handle XCode/Eclipse for Android/iOS development?
The question is quite opinion based. Can it handle development - absolutely. Will it be fast enough - now that's a matter of your personal reception of "fast enough".

The MacBook is quite a capable machine. It will run Development-Tools without any issues. It will perform lower than a MacBook Pro CPU and GPU-wise, so it really depends on your personal needs. Use something like Activity Monitor to keep an eye on your current system load during your daily tasks. If your machine is often at it's limits, you will have to take sacrifices with a MacBook. If your machine idles a lot and is only pushed to the edge rarely, you'll probably be happy with the machine.