CompilingTime

using UnityEditor;
using UnityEngine;

[InitializeOnLoad]
static class Compiling {

    private static bool isCompiling {
        set { EditorPrefs.SetBool("IsCompiling", value); }
        get { return EditorPrefs.GetBool("IsCompiling"); }
    }
    private static double lastTimeCompiling {
        set { EditorPrefs.SetString("LastTimeCompiling", value.ToString()); }
        get { return double.Parse(EditorPrefs.GetString("LastTimeCompiling", EditorApplication.timeSinceStartup.ToString())); }
    }
    private static double compiledTime {
        get { return EditorApplication.timeSinceStartup - lastTimeCompiling; }
    }

    static Compiling() {
        EditorApplication.update += () => {
            if(EditorApplication.isCompiling == isCompiling)
                return;

            if(isCompiling = EditorApplication.isCompiling)
                lastTimeCompiling = EditorApplication.timeSinceStartup;
            else if(compiledTime > 0d)
                Debug.LogFormat("Compiled in {0} seconds", compiledTime.ToString("0.00"));
        };
    }
}