PostBuildProcess.cs

using UnityEngine;
using UnityEditor;
using UnityEditor.Callbacks;
using UnityEditor.iOS.Xcode;
using System.Collections;
using System.IO;

public class PostBuildProcess
{
	internal static void CopyAndReplaceDirectory (string srcPath, string dstPath)
	{
		if (Directory.Exists (dstPath))
			Directory.Delete (dstPath);
		if (File.Exists (dstPath))
			File.Delete (dstPath);
		
		Directory.CreateDirectory (dstPath);
		
		foreach (var file in Directory.GetFiles(srcPath))
			File.Copy (file, Path.Combine (dstPath, Path.GetFileName (file)));
		
		foreach (var dir in Directory.GetDirectories(srcPath))
			CopyAndReplaceDirectory (dir, Path.Combine (dstPath, Path.GetFileName (dir)));
	}

	[PostProcessBuild]
	public static void OnPostProcessBuild (BuildTarget buildTarget, string path)
	{
		if (buildTarget == BuildTarget.iOS) {
			ProcessForiOS (path);
		}
	}

	private static void ProcessForiOS (string path)
	{
		string pjPath = path + "/Unity-iPhone.xcodeproj/project.pbxproj";
		PBXProject pj = new PBXProject ();
		pj.ReadFromString (File.ReadAllText (pjPath));

		string target = pj.TargetGuidByName ("Unity-iPhone");

		pj.SetBuildProperty (target, "CLANG_ENABLE_MODULES", "YES");

		File.WriteAllText (pjPath, pj.WriteToString ());
	}

}