CMakeLists.txt调用g2o优化库，解决找不到某些库文件问题

解决生成的程序在运行时找不到某些链接库的错误：error while loading shared libraries: libg2o_stuff.so: cannot open shared object file: No such file or directory: 1. 将g2o安装到系统目录下，2. 并且在/etc/ld.so.conf中添加库的路径 /usr/local/lib

1. 编译安装g2o.
   项目地址：https://github.com/RainerKuemmerle/g2o
   编译完成后，需要执行sudo make install安装到系统目录下。
2. 在/etc/ld.so.conf中添加库的路径

   sudo gedit /etc/ld.so.conf
   

   加入以下路径：

   /usr/local/lib
   

   执行

   sudo ldconfig
   

3. 编写CMakeLists.txt文件，通过FindG2O.cmake找到该库。

   cmake_minimum_required(VERSION 3.14)
   project(g2oDemo)
   
   IF(NOT CMAKE_BUILD_TYPE)
     SET(CMAKE_BUILD_TYPE Release)
   ENDIF()
   MESSAGE("Build type: " ${CMAKE_BUILD_TYPE})
   
   list(APPEND CMAKE_MODULE_PATH g2o路径/cmake_modules)
   
   # C++14 support
   set(CMAKE_CXX_STANDARD 14)
   set(CMAKE_CXX_STANDARD_REQUIRED ON)
   
   find_package(Eigen3 3.3 REQUIRED)
   find_package(G2O REQUIRED)
   include_directories(${G2O_INCLUDE_DIR})
   message(STATUS "G2O_INCLUDE_DIR: ${G2O_INCLUDE_DIR}")
   message(STATUS "G2O_FOUND: ${G2O_FOUND}")
   
   SET(G2O_LIBRARIES ${G2O_STUFF_LIBRARY} ${G2O_CORE_LIBRARY} ${G2O_CLI_LIBRARY} ${G2O_SOLVER_CHOLMOD} ${G2O_SOLVER_CSPARSE} ${G2O_SOLVER_CSPARSE_EXTENSION} 
   ${G2O_SOLVER_DENSE} ${G2O_SOLVER_PCG} ${G2O_SOLVER_SLAM2D_LINEAR} ${G2O_SOLVER_STRUCTURE_ONLY} ${G2O_SOLVER_EIGEN} ${G2O_TYPES_DATA} ${G2O_TYPES_ICP} ${G2O_TYPES_SBA}
   ${G2O_TYPES_SCLAM2D} ${G2O_TYPES_SIM3} ${G2O_TYPES_SLAM2D} ${G2O_TYPES_SLAM3D})
   
   add_executable(ba_demo ba_demo.cpp)
   target_link_libraries(ba_demo ${G2O_LIBRARIES})
   

   编译运行即可。