Though I would post this one since I did experience a few issues attempting to install jekyll, including this "Failed to build gem native extension" annoying error.
Right, so you have it all installed. So you think. As advised on the jekyll site, you’ve done your:
sudo gem update --system
Xcode and its command line tools are in there, but you still get an error while running:
sudo gem install jekyll
Building native extensions. This could take a while... ERROR: Error installing jekyll: ERROR: Failed to build gem native extension.
It appears that the installation order is vital, and therefore you should try to uninstall ruby, start from a clean situation, and reinstall it.
It did fix it for me, so have a try if you’re stuck and you’re a numpty like me when it comes down to gems, CLI, and the rest.
rvm get head rvm reset
Then check what’s in there with:
Note what ruby version is installed, in my case it was ruby-2.0.0-p247.
rvm remove ruby-2.0.0-p247 rvm cleanup rvm repair
Only then go with:
sudo gem update --system sudo gem install jekyll
Hope this helps.