os/mac/utils/bottles: support ARM bottles.

[MikeMcQuaid]

This will be eventually needed for Big Sur.

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[sjackman]

On Linux (and generic) the order of this two-tuple is CPU_OS.

brew/Library/Homebrew/utils/bottles.rb

Lines 8 to 10 in 1ff10f9

	def tag
	@tag ||= "#{ENV["HOMEBREW_PROCESSOR"]}_#{ENV["HOMEBREW_SYSTEM"]}".downcase.to_sym
	end

Should macOS use this same order for consistency?

[MikeMcQuaid]

I'm fine with whatever.

[sjackman]

Opened PR #7942