Change the shader of a building to Default in asset editor.

ShaderChange_Building_Default.cs

var shader = Shader.Find("Custom/Buildings/Building/Default");
var asset = ToolsModifierControl.toolController.m_editPrefabInfo as BuildingInfo;
if(asset.m_material != null) asset.m_material.shader = shader;
if(asset.m_lodMaterial != null) asset.m_lodMaterial.shader = shader;
asset.m_requireHeightMap = false;