Correct... but many ruby gems and node.js modules compile using gcc. (v8 being the most annoying one for us)
are you sure it's actually gcc and not clang, because "gcc" on OS X is clang
It's doing gcc 4.2, and when you try to install / compile a higher version it fails. Pretty sure.
I've had luck installing most Ruby gems used by my projects. The only exception so far has been Nokogiri, and even in that case there were instructions on the project's web page that got it to install without a hitch.