[defaults] Update minimum required cmake version.

This is done to be consistent with the required version in
the common-superbuild.

CMakeLists.txt

-cmake_minimum_required(VERSION 2.8.8)
+cmake_minimum_required(VERSION 3.12)
 
 project(LidarViewSuperBuild)
 set (SuperBuild_CMAKE_DIR "${CMAKE_CURRENT_SOURCE_DIR}/CMake")