Add aarch64-linux support

[Nasafato]

No issue, but related to #913. wasm-opt does include pre-built binaries for aarch64-linux, so we add a conditional to handle that case. Let me know if you still want me to create an issue

• [x] You have the latest version of rustfmt installed
• [x] You ran cargo fmt on the code base before submitting
• [x] You reference which issue is being closed in the PR text

[yaleman]

Any chance this can be merged? It's still a problem.

[wegylexy]

What about Windows on ARM?