Installing MySQL native extensions on OS X using existing MacPorts MySQL
on Saturday 8th December, 2007 Gabe speculated thusly…Getting these native extensions from Ruby gems to build and install has been a bit of a nightmare. Especially since MySQL, Apache, Ruby, etc were compiled from source using MacPorts (which I heartily recommend).
The answer was as simple as:
sudo gem install mysql -- --with-mysql-config=/path/to/your/mysql/bin/mysql_config