You can make a script that you attach to a single game object (for which there's just going to be one instance) and you put the following code in the Start function of the script :

void Start()
{

            UnityEngine.Object[] characterControllers = GameObject.FindObjectsOfTypeAll(typeof(CharacterController));

            System.Collections.ArrayList existingCCColliders = new System.Collections.ArrayList();

            foreach (CharacterController charController in characterControllers)
            {
                Component[] colliders = charController.GetComponents(typeof(Collider));

                foreach (Collider collider in colliders)
                {
                    foreach (Collider existingCollider in existingCCColliders)
                    {
                        Physics.IgnoreCollision(collider, existingCollider);
                    }
                }
            }
}

Now there are probaly bugs in this http://code.It's just the logic, I haven't tested it. But the idea should work. and maybe you'll have to replace the arraylist by some other type of collection as I don't remember if arraylists are supported in Indie.

function Start() {
        ignoreCollision("Player");
}

function ignoreCollision(tag: String) {
    var objects = GameObject.FindGameObjectsWithTag(tag);
    for (o in objects) {
        if (o.GetComponent("Collider") && o != gameObject) Physics.IgnoreCollision(collider, o.collider);
    }
}

just editing the post above me.