Add OS detection and associated errors

[natemcintosh]

Goal

Instead of assuming that the tool is being run on Linux, check what the OS actually is, and provide an error if it is not Linux. (Working non-Linux versions could eventually happen).

Context

Currently, duckup simply assumes it is being run Linux, and downloads a Linux binary. It should instead fail on any platforms that are not Linux.

Required features

• Can detect if OS is macOS or Windows
• Errors out for mac and Windows (for now)

Specifications

• An early check of the OS in main()
• An early failure if not running on Linux

Related documents

• os_info crate