Mark the GameObject as a Static Occluder in the occlusion culling system.
For more information, see the documentation on the Occlusion Culling system.
void StaticEditorFlagsExample()
{
    // Create a GameObject
    var go = new GameObject("Example");
    // Set the GameObject's StaticEditorFlags
    var flags = StaticEditorFlags.OccluderStatic;
    GameObjectUtility.SetStaticEditorFlags(go, flags);
}