cerbero: Add rust support for MSVC ARM64

Hi all,

This MR is to re-enable Windows ARM64 support. The only bit that was missing was the Rust triplet.

I did not add a triplet for MinGW because I couldn't find any yet-- it seems the triplet will be aarch64-pc-windows-gnullvm but that is Tier 3 still. https://doc.rust-lang.org/rustc/platform-support/pc-windows-gnullvm.html