Failed to build gem native extension
The problem is that in Lion Xcode 4.3 doesn't by default install (or even include) the command-line tools such as gcc - and those are what are needed here. In the Downloads pane of Xcode's prefs, under Components, ask for the command-line tools. (See the readme: https://developer.apple.com/library/content/documentation/DeveloperTools/Conceptual/WhatsNewXcode/Chapters/xcode_4_0.html#//apple_ref/doc/uid/TP40016147-SW35)
Actually I believe you didn't need to install Xcode at all, since in fact the command-line tool can now be downloaded and installed separately.
I already had Command-line tools installed (xCode as well)... and still had this (initial) error.
The problem was that xCode and the command line tools are no longer installing the gcc compiler. I don't know when they stopped shipping it, but I run mountain lion, and it's not here.So what eventually solved my problem was installing gcc from scratch (https://github.com/kennethreitz/osx-gcc-installer).
Keep Smiling :)
If someone has the same problem for Ubuntu Linux, the solution was:
sudo apt-get install build-essentialsudo apt-get install libsqlite3-dev