RVM Ruby 1.9.1 install can’t locate zlib but its runtime and dev library are there

Use rvm to install zlib

https://rvm.io/packages/zlib/

rvm package install zlib
rvm remove 1.9.1
rvm install 1.9.1 -C --with-zlib-dir=$rvm_path/usr

Edit: The rvm package command was renamed to rvm pkg in v1.6.25.