neovim: build with luajit on `aarch64-linux`
neovim: build with luajit on `aarch64-linux`

https://github.com/NixOS/nixpkgs/pull/129543 disabled building neovim
with luajit on all `aarch64` platforms, however, building neovim with
luajit on `aarch64-linux` builds successfully, and avoids various issues
I encountered with some Lua-based plugins.

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