使用HomeBrew，例如：$ brew link cmake，会出现一下错误。
Could not symlink share/man/man7/cmake-buildsystem.7 /usr/local/share/man/man7 is not writable.
解决方法：
先执行 $ sudo chown -R $(whoami):admin /usr/local/share/man
后执行 $ brew link cmake
即可。
Homebrew: Could not symlink, /usr/local/share/man/man7 is not writable