Getting the following error on Mac OS X? Read on.
fsevent/fsevent_watch.c:1:10: fatal error: 'stdio.h' file not found
XCode 4.3 and later does not install unix tools, so the usual header files are missing.
The following bit of magic is needed:
sudo xcode-select -switch /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/
Re-run your gem install / bundle and it should work now.