[MCU BOOT] Missing dependency out-of-the-box for macos

[luizvilla]

Describe the bug
While helping a colleague get throught the "Getting Started" page with her macos, I came accross an error.
The error was relative to :

missing lzma package

We manage to solve it by doing :

brew install xz

This should not be the case, it should work out-of-the-box.

To Reproduce
Steps to reproduce the behavior:

1. Follow the installation procedure in 'Getting Started' for MACOS
2. Download the voltage mode buck code
3. Build
4. See error

Expected behavior
A normal build process with a SUCCESS at the end.

Desktop (please complete the following information):

• OS: iOS 15.XX
• Version: Core version V1.0