I'm trying to install litch on mac.

I have followed the instructiosn on https://gswiki.play.net/Mac_Installa...ich_(software)

I downloaded the diagnostic tool and the installer. I've run the isntaller program and everything is installed except gtk2 is not present.

When i run the install program it says

sqlite3 checkpoint finished in 13 sec from script start
Gem gtk2 is not installed. ✘
Installing gtk2 and related dependencies.

Building native extensions. This could take a while...
ERROR: Error installing gtk2:
ERROR: Failed to build gem native extension.

Any input?