Build pre- and post-processing. Workaround for missing build canceled delegate.

BuildHandler.cs

using System;
using UnityEditor;
using UnityEditor.Build;
using UnityEngine;
using Object = UnityEngine.Object;

[InitializeOnLoad]
public class BuildHandler : MonoBehaviour
{
	/// <summary>
	/// This is invoked, before any Unity build steps are taken,
	/// this means also before e.g. <see cref="IPreprocessBuildWithReport"/>.<para/>
	/// In the case of an <see cref="Exception"/>, invocation is interrupted,
	/// the build is not even started. but <see cref="OnBuildCleanup"/>
	/// is still invoked on every delegate.
	/// </summary>
	public static event Action OnBuildStarted;
	/// <summary>
	/// Finally, this is invoked after a build completed <b>or</b> failed.
	/// This can be used to clean up any build artifacts. If the build failed,
	/// <see cref="IPostprocessBuildWithReport"/> isn't called, so this event
	/// can be used as a workaround. <see cref="Exception"/>s are caught per invocation, so
	/// it's guaranteed, that every delegate is invoked.
	/// </summary>
	public static event Action OnBuildCleanup;

	static BuildHandler()
	{
		BuildPlayerWindow.RegisterBuildPlayerHandler(Build);
	}

	private static void Build(BuildPlayerOptions buildOptions)
	{
		try
		{
			BuildStarted();

			//now start Unity's default building procedure
			BuildPlayerWindow.DefaultBuildMethods.BuildPlayer(buildOptions);
		}
		catch (BuildPlayerWindow.BuildMethodException) { } //logged internally
		catch (Exception ex)
		{
			Exception log = ex.InnerException == null ? ex : ex.InnerException;
			Debug.LogException(log);
			Debug.LogErrorFormat("{0} in BuildHandler: '{1}'", log.GetType().Name, ex.Message);
		}
		finally
		{
			BuildCleanup();
		}
	}

	private static void BuildStarted()
	{
		try
		{
			OnBuildStarted?.Invoke();
		}
		catch (Exception ex)
		{
			throw new Exception("OnBuildStarted failed", ex);
		}
	}

	private static void BuildCleanup()
	{
		if (OnBuildCleanup != null)
		{
			foreach (Action cleanupBuild in OnBuildCleanup.GetInvocationList())
			{
				try
				{
					cleanupBuild.Invoke();
				}
				catch (Exception ex)
				{
					Object context = cleanupBuild.Target as Object;
					Debug.LogException(ex, context);
					Debug.LogWarning("Caught exception while BuildHandler.OnBuildCleanup... Continuing");
				}
			}
		}
	}
}