[libpng]could not link symlink include/libpng16

问题：

➜  ~  brew link libpng
Linking /usr/local/Cellar/libpng/1.6.17...
Error: Could not symlink include/libpng16/png.h
Target /usr/local/include/libpng16/png.h
already exists. You may want to remove it:
  rm '/usr/local/include/libpng16/png.h'
To force the link and overwrite all conflicting files:
  brew link --overwrite libpng
To list all files that would be deleted:
  brew link --overwrite --dry-run libpng

解决办法：

sudo chmod -R 777 /usr/local/include/libpng16
brew link --overwrite libpng