Support `aarch64-unknown-linux-gnu` configuration

[l2dy]

aarch64 support is currently only available on macos. It should be possible to extend that to Linux as well.

treesit-langs/treesit-langs.el

Lines 242 to 250 in 2594bd9

	(format "tree-sitter-grammars.%s.v%s.tar%s"
	;; FIX: Implement this correctly, refactoring 'OS' -> 'platform'.
	(pcase os
	("windows" "x86_64-pc-windows-msvc")
	("linux" "x86_64-unknown-linux-gnu")
	("freebsd" "x86_64-unknown-freebsd")
	("macos" (if (string-prefix-p "aarch64" system-configuration)
	"aarch64-apple-darwin"
	"x86_64-apple-darwin")))

Prerequisite: emacs-tree-sitter/tree-sitter-langs#305