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
這樣文件會被默認安裝到/usr/local/include/eigen3，但大多數包的默認路徑是/usr/include/eigen3,所以安裝前修改路徑