feat: allow font install on linux

[SMillerDev]

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This should disable quarantine on Linux, allow installing fonts and set a location for the fonts. Marking this as draft until I've had a moment to test it.

Waiting for #18808 to be merged

[SMillerDev]

Installing fonts now works, although it is still installing in the macOS location. I can't get the DEFAULTS to work.

[SMillerDev]

@Homebrew/brew I can't get the code to pick up this extended version, no matter what I try. Does anyone have a suggestion how to do that?

[MikeMcQuaid]

@dduugg may know!

[dduugg]

Ugh, guilty 😬

prepending (like include) only affects instance methods. If I understand what you're trying to do here, you'll want to write this as an instance method in a submodule (e.g. ClassMethods) which is then prepended to the singleton class. See Keg for an example of this dual-prepend approach, specifically:

brew/Library/Homebrew/extend/os/mac/keg.rb

Lines 130 to 131 in e23d079

	Keg.singleton_class.prepend(OS::Mac::Keg::ClassMethods)
	Keg.prepend(OS::Mac::Keg)

(I'm entirely to blame for this convoluted mess, and I'm open to alternatives. It's probably useful to document this for others, maybe in Typechecking.md, though it has discoverability issues.)

[dduugg]

It's a stylistic choice until I get around to writing a linter rule, but I like these as endless defs, since they are pseudo-constants. (It also saves some vertical real estate.):

Suggested change

	def self.available?
	false
	end
	def self.available? = false

[dduugg]

Is this equivalent logic? (The triple negative of unless/reject/empty? hurts my tiny 🧠)

Suggested change

	raise ::Cask::CaskError, "macOS is required for this software." unless artifacts.reject do |k|
	k.is_a?(::Cask::Artifact::Font)
	end.empty?
	raise ::Cask::CaskError, "macOS is required for this software." if artifacts.any? do |k|
	k.is_a?(::Cask::Artifact::Font)
	end