In the Build Settings dialog there is a check box called "Development Build".

If it is checked isDebugBuild will be true. In the editor isDebugBuild always returns true. It is recommended to remove all calls to Debug.Log when deploying a game, this way you can easily deploy beta builds with debug prints and final builds without.

	// Log some debug information only if this is a debug build
	if (Debug.isDebugBuild) {
		Debug.Log ("This is a debug build!");
	}

using UnityEngine;
using System.Collections;

public class Example : MonoBehaviour {
    void Example() {
        if (Debug.isDebugBuild)
            Debug.Log("This is a debug build!");
        
    }
}

import UnityEngine
import System.Collections

public class Example(MonoBehaviour):

	def Example() as void:
		if Debug.isDebugBuild:
			Debug.Log('This is a debug build!')