brew安裝錯誤:/usr/local/include is not writable

在Mac上使用brew命令安裝東西，提示/usr/local/include is not writable的錯誤，在Stack Overflow很快找到解決辦法：

Simple solution that worked for me:

1. click on your background to go to finder
2. click on go and go to folder /usr
3. right click on local and do get info
4. unlock the lock at the bottom
5. click + sign and add your user to the list and give read/write privileges
6. click on the gear sign at the bottom and choose apply to enclosed items to recurse under that directory and assign privileges too all directories beneath it.

OK，大功告成，現在可以正常使用brew了。