message: Add BUILD_DEMO option to CMakeLists.txt
diff: project(meshoptimizer)
  cmake_minimum_required(VERSION 3.4)
  +option(BUILD_DEMO "Build demo" OFF)
  +
  set(CMAKE_CXX_STANDARD 11)
  set(SOURCES
  @@ -15,5 +17,7 @@ set(SOURCES
  add_library(meshoptimizer STATIC ${SOURCES})
  +if(BUILD_DEMO)
  add_executable(demo demo/main.cpp demo/tiny_obj_loader.cpp)
  target_link_libraries(demo meshoptimizer)
  +endif()
  