When executing gem install jekyll on OSX 10.8 with the standalone Command Line Tools package from Apple\'s Developer site installed (no Xcode), i run into the follo
gem install jekyll
Even with Command Line Tools installed, your xcode-select is strange. It should be pointing into your XCode bundle, not /usr/bin:
/usr/bin
$ xcode-select -print-path /Applications/Xcode.app/Contents/Developer
Switch it to Xcode like this:
$ sudo xcode-select --switch /Applications/Xcode.app