Generating builds from scripts in Unity

ChangePCStore.cs

#if UNITY_STANDALONE && !STEAM_BUILD
  [MenuItem("Build/Switch to Steam")]
#endif
  public static void SwitchToSteam() {
    string defines = PlayerSettings.GetScriptingDefineSymbolsForGroup(BuildTargetGroup.Standalone);
    defines = AddCompilerDefines(defines, "STEAM_BUILD");
    defines = RemoveCompilerDefines(defines, "GOG_BUILD");

    UnityEngine.Debug.Log("Compiling with DEFINE: '" + defines + "'");
    PlayerSettings.SetScriptingDefineSymbolsForGroup(BuildTargetGroup.Standalone, defines);
  }

#if UNITY_STANDALONE && !GOG_BUILD
  [MenuItem("Build/Switch to GOG")]
#endif
  public static void SwitchToGOG() {
    string defines = PlayerSettings.GetScriptingDefineSymbolsForGroup(BuildTargetGroup.Standalone);
    defines = AddCompilerDefines(defines, "GOG_BUILD");
    defines = RemoveCompilerDefines(defines, "STEAM_BUILD");

    UnityEngine.Debug.Log("Compiling with DEFINE: '" + defines + "'");
    PlayerSettings.SetScriptingDefineSymbolsForGroup(BuildTargetGroup.Standalone, defines);
  }

#if UNITY_STANDALONE && (STEAM_BUILD || GOG_BUILD)
  [MenuItem("Build/Switch to No Platform")]
#endif
  public static void SwitchToNoPlatform() {
    string defines = PlayerSettings.GetScriptingDefineSymbolsForGroup(BuildTargetGroup.Standalone);
    defines = RemoveCompilerDefines(defines, "STEAM_BUILD", "GOG_BUILD");

    UnityEngine.Debug.Log("Compiling with DEFINE: '" + defines + "'");
    PlayerSettings.SetScriptingDefineSymbolsForGroup(BuildTargetGroup.Standalone, defines);
  }

  private static string AddCompilerDefines(string defines, params string[] toAdd){
    List<string> splitDefines = new List<string>(defines.Split(new char[] { ';' }, System.StringSplitOptions.RemoveEmptyEntries));
    foreach (var add in toAdd)
      if (!splitDefines.Contains(add))
        splitDefines.Add(add);

    return string.Join(";", splitDefines.ToArray());
  }

  private static string RemoveCompilerDefines(string defines, params string[] toRemove){
    List<string> splitDefines = new List<string>(defines.Split(new char[] { ';' }, System.StringSplitOptions.RemoveEmptyEntries));
    foreach(var remove in toRemove)
      splitDefines.Remove(remove);

    return string.Join(";", splitDefines.ToArray());
  }