Don’t click Update if you have El Capitan

This is missing the command line tools necessary to work on OS X El Capitan. Your old command line tools will start to give you errors like this:
ld: file not found: /usr/lib/system/libsystem_symptoms.dylib for architecture x86_64

This will break homebrew and just about anything on your system that compiles things from source.

MrNerdFabulous about Xcode, v8.1