EmulatorPkg: Unix: Use XCODE5 and lldb if Xcode 5 is detected

EmulatorPkg: Unix: Use XCODE5 and lldb if Xcode 5 is detected

The EmulatorPkg build.sh will use XCODE5 if that is the default toolchain, and
default to using lldb if Xcode 5 is dectect. This will work for Xcode 6 and
possibly future version of Xcode too.

/usr/bin/clang is just a wrapper that calls the currently selected Xcode
version. xcode-select is used used to display or set the current version of
Xcode used by the command line tools.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Anderw Fish <afish@apple.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
git-svn-id: https://svn.code.sf.net/p/edk2/code/trunk/edk2@15983 6f19259b-4bc3-4df7-8a09-765794883524