Add new action to finalise existing Xcode installation

[NickAb]

Hi,

I am looking into optimising my Xcode deployment script used to install Xcode to tens of machines.

Currently it does something like:

1. rsync xcode.xip file from base host to all other hosts to /xcode.xip
2. run xcversion install 9.2 --no-switch --url=file:///xcode.xip

But my understanding is that I can save a lot of time on unpacking xip file, if I unpack it once on a base host and rsync Xcode.app directly. And then all I will need to do is to run following lines of install action: https://github.com/KrauseFx/xcode-install/blob/e7e5441d250e98209d6cd56b7c6b36f396483170/lib/xcode/install.rb#L129-L132

Is it correct and would you be open to a PR that will add new action called, for example, prepare or run-first-launch which will run approve_license and install_components for selected xcode version?

[timsutton]

I can see the value in having that, if you're otherwise rolling your own mechanism to distribute the app bundle. Feel free to write up a PR!