$ brew install erlang
Error: You must `brew link libtool' before erlang can be installed
zhi:~ zhi$ brew link libtool
Linking /usr/local/Cellar/libtool/2.4.2...
Error: Could not symlink include/ltdl.h
/usr/local/include is not writable.
解决办法
sudo chown -R whoami /usr/local
brew link libtool