last: fix some hostnames are not shown properly with --hostname option issue 212

[LionelMeli]

No description provided.

[sylvestre]

could you please add a test to make sure we don't regress? thanks

[Copilot]

PR Overview

This PR addresses an issue where the hostname is not displayed properly when using the --hostname option by refactoring the formatting logic.

• Reformats the time and end time output by replacing a computed width with fixed-width fields.
• Moves the hostname output to a separate conditional block to ensure it is printed correctly when required.

Reviewed Changes

File	Description
src/uu/last/src/platform/unix.rs	Adjusts formatting logic for time, end time, and hostname output.

Copilot reviewed 1 out of 1 changed files in this pull request and generated no comments.

Comments suppressed due to low confidence (2)

src/uu/last/src/platform/unix.rs:525

• [nitpick] Consider replacing the magic number 12 with a named constant for clarity and maintainability.

write!(buf, " {time:<12}").unwrap_or_default();

src/uu/last/src/platform/unix.rs:526

• [nitpick] Consider replacing the magic number 18 with a named constant for clarity and maintainability.

write!(buf, " {end_time_delta:<18}").unwrap_or_default();

[LionelMeli]

Hello,

the last command doesn't work in mac OS and as I understand cannot work per this post:
https://unix.stackexchange.com/questions/468846/macos-what-file-does-the-command-last-get-its-information-from
and this one: https://superuser.com/questions/128705/ssh-last-login-last-and-os-x#:~:text=It%20seems%20modern%20Mac%20OS which explains " It seems modern Mac OS X records utmp/wtmp/lastlog-like information in the Apple SysLog (asl) database files at /var/log/asl/*."
In fact, after created a Mac OS VM (ventura thanks to quickemu project), the file /var/run/utmpx contains only the 2 entries (overwritten at each login). The uucore::utmpx::Utmpx doesn't fit the Mac OS requierement.

Maybe better to restrict the last command to the (true) *Nix platform? Let's me know.

[LionelMeli]

Hello @sylvestre,
Could I do the same thing as per this PR: #234 (so mark things as unimplemented for systems other than Linux such as macOS)?