If you encounter errors like this ``fatal error: 'stdlib.h' file not foundon Yosemite and Xcode 6.0.1, your
/usr/include/` is probably missing.
Try this command on Terminal:
sudo ln -s /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include /usr/include