Simple compilation time for Unity. Just pop it into an Editor folder and it should give you a simple output of how long it took to compile your code each time.

CompilationTimer.cs

using System;
using UnityEngine;
using UnityEditor;

namespace instance.id.Editor
{
    [InitializeOnLoad]
    class CompilationTimer : EditorWindow
    {
        static bool isTrackingTime;
        static double startTime;

        static CompilationTimer()
        {
                EditorApplication.update += Update;
                        startTime = PlayerPrefs.GetFloat("CompileStartTime", 0);
            if (startTime > 0)
            {
                isTrackingTime = true;
                
            }
        }

        static void Update()
        {
            if (EditorApplication.isCompiling && !isTrackingTime)
            {
                startTime = EditorApplication.timeSinceStartup;
                PlayerPrefs.SetFloat("CompileStartTime", (float)startTime);
                isTrackingTime = true;
            }
            else if (!EditorApplication.isCompiling && isTrackingTime)
            {
                var finishTime = EditorApplication.timeSinceStartup;
                isTrackingTime = false;
                var compileTime = finishTime - startTime;
                PlayerPrefs.DeleteKey("CompileStartTime");
                var timeStamp = DateTime.Now.ToString("hh:mm:ss");
                Debug.Log("Script compilation length: " + compileTime.ToString("0.000") + "s\n" +
                                   "Current time: " + timeStamp);
            }
        }
    }
}