Generate a NavMesh in runtime

The only thing i need to know is, if its possible to make a navigation mesh without using the “using UnityEditor;” in runtime or if its possible to store a NavMesh inside a prefab.
this is the script that creates a NavMesh in runtime, wich does use “using UnityEditor;” (since it uses that line, it can not be compiled in the build).

using UnityEditor;
using UnityEngine;
using System.Collections;
public class AddNavMesh : MonoBehaviour {

	void Start()
	{
		NavMeshBuilder.BuildNavMesh();
	}
}

if possible also explain how :3?

With the current system in Unity 4.3.4 it is not possible to do this.