脚本触发器
country_can_build_in_location
调用它的脚本会填入这些值，各调用处见“关联”。
$building_type$$location$
没有指向其他条目的链接。
custom_description = {
text = country_can_build_in_location_text
value = building_type:$building_type$
object = $location$
can_build_building = building_type:$building_type$
$location$ = {
can_build_building = building_type:$building_type$
}
}