https://blog.csdn.net/xiangxianghehe/article/details/81236299
sudo cp -r /usr/local/include/eigen3 /usr/include
sudo cp -r /usr/local/include/Eigen /usr/include
sudo updatedb
这样文件会被默认安装到/usr/local/include/eigen3，但大多数包的默认路径是/usr/include/eigen3,所以安装前修改路径
