Question: Trying to diagnose a work development laptop... What version of Clang and GCC come standard with OSX 10.10 Yosemite?

This is what I have on my Mavericks... machine, will respond with my home iMac when it boots.

```
which clang
/usr/bin/clang

which gcc
/usr/bin/gcc

clang --version
Apple LLVM version 4.2 (clang-425.0.27) (based on LLVM 3.2svn)
Target: x86_64-apple-darwin13.4.0
Thread model: posix

gcc --version
i686-apple-darwin11-llvm-gcc-4.2 (GCC) 4.2.1 (Based on Apple Inc. build 5658) (LLVM build 2336.11.00)
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

```

Answer: 
Try running: `xcode-select --install`, followed by: `xcodebuild -license`
After many failed attempts at updating the C Compilers, we did a fresh install of Yosemite and it was fixed.

Not a great solution, but without trying to hand build Clang the sane as Mac native it was the only solution.