Merge: Test compilation of OS X and iOS programs, on OS X

The results of the compilation of iOS apps by XCode are directories. This PR fix tests.sh to detect those directory and report them cleanly.

Also intro a script for running OS X specific tests.

Pull-Request: #1232
Reviewed-by: Jean Privat <jean@pryen.org>
Reviewed-by: Alexandre Terrasa <alexandre@moz-code.org>