Installation Issues

If you have Xcode 4.3, a Ruby installed with RVM, and installation fails with the following message:

checking for -std=c99 option to compiler... *** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.

Then re-install Ruby like so:

$ rvm install 1.9.3 --with-gcc=clang