Allow building aarch64 (Large VM, Debian) for a rpi4 deployment

[NickJLange]

Summary

I'm not sure why the current build script has the current logic, but to compile on an aarch64 VM for deployment to a rpi4, we need to use the right cross-compiler. This fixes the selection. Hopefully in dialogue the original logic will emerge.

Test plan

Built on a Debian Bookworm VM (Large) for deployment to a Debian RPI4 (Small)

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[Copilot]

Pull request overview

This PR fixes the cross-compiler selection logic to enable building on aarch64 VMs (like Debian Bookworm Large) for deployment to Raspberry Pi 4 devices. The original code incorrectly mapped aarch64 hosts to use x86_64 cross-compilers, preventing proper compilation.

Changes:

• Separated aarch64 architecture detection into its own case to correctly download aarch64-hosted cross-compilers
• Removed aarch64 from the x86_64 architecture group

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[Copilot]

Pull request overview

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