Specify Homebrew dependencies with a Brewfile

[FtZPetruska]

This PR adds a Brewfile at the top of the repository to handle Homebrew dependencies more conveniently.

This has the advantage of:

• Having all the macOS dependencies listed in a single location, instead of having it duplicated in the build guide and CI.
• Installing everything in a single command without listing every packages (brew bundle).
• For CI, this fixes warnings about trying to install the dependencies already pre-installed on the runner.

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I have also updated the macOS build guide, so it recommends brew bundle to install dependencies. Also took the opportunity to update the option name since ENABLE_LTO was removed, and to recommend using cpack to create a package instead of manually baking a release.

[Pedro-Beirao]

All very good thank you!
I didnt even know brew bundle was a thing. Never seen any other project using it.

[FtZPetruska]

I didnt even know brew bundle was a thing. Never seen any other project using it.

I only stumbled upon it recently. I saw projects such as vorbis or opusfile use it, read about it and thought it would be a nice fit to handle macOS dependencies.