Detect if Xcode Command Line Tools is installed (or not)

Not having this installed can cause lots of issues on iOS, and today, even stopped a Mac build from happening.

http://community.stencyl.com/index.php/topic,25893.new.html#new

We should figure out a way to definitively check for its existence. Maybe just run one of the commands it enables and parse the response?

Actually, you can just check for the version number. In the Terminal, it's done like this...

$ xcode-select -version

It will return...

xcode-select version 2339.

At least some sort of version number if it's installed.

In your code, you should be able to run a terminal command that does this silently without actually opening the terminal and reading/checking for a version number.  All I have is the command line tools installed in 10.6.8 and 10.10.5. The terminal command works on both.

This was fixed about a month ago. I'll move this to completed.