●BuildSettingで設定しているプラットフォーム
　EditorUserBuildSettings.activeBuildTarget

　・ログ表示
　Debug.Log(EditorUserBuildSettings.activeBuildTarget.ToString());

　・enum

using System;

namespace UnityEditor
{
    public enum BuildTarget
    {
        StandaloneOSXUniversal = 2,
        StandaloneOSXIntel = 4,
        StandaloneWindows = 5,
        WebPlayer = 6,
        WebPlayerStreamed = 7,
        iPhone = 9,
        PS3 = 10,
        XBOX360 = 11,
        Android = 13,
        StandaloneGLESEmu = 14,
        NaCl = 16,
        StandaloneLinux = 17,
        FlashPlayer = 18,
        StandaloneWindows64 = 19,
        MetroPlayer = 21,
        StandaloneLinux64 = 24,
        StandaloneLinuxUniversal = 25,
        WP8Player = 26,
        StandaloneOSXIntel64 = 27,
        BlackBerry = 28,
        [Obsolete("Use BlackBerry instead")]
        BB10 = 28,
        Tizen = 29,
        PSP2 = 30,
        PS4 = 31,
        PSM = 32,
        XboxOne = 33,
        SamsungTV = 34,
    }
}