Well, at least trying to run "cc" has prompted it to try to install the command-line developer tools, which is all I wanted anyways. I just hope that estimated 80-hour download time is wrong.

On the plus side, it's taken less than 40 hours for the progress bar to make it past the half-way mark. On the minus side, the progress bar hasn't moved for the last little while, and is no longer giving a time estimate.

Finally installed. Why is macOS so hard to use? I prefer being able to just "apt install gcc".