Cross-compilation

[cryptoquick]

Possible targets:

• [ ] x86_64-unknown-linux-gnu
• [ ] x86_64-unknown-linux-musl
• [ ] x86_64-apple-darwin
• [ ] x86_64-pc-windows-gnu
• [ ] aarch64-unknown-linux-gnu
• [ ] aarch64-unknown-linux-musl

Also:

• [ ] Manually tested on platforms
• [ ] Integrates with #83

At some point investigate platform-specific integration testing.