samples: doc: Added README for POSIX samples

[dougwfoster]

Added README.rst for eventfd and uname POSIX samples.
Helps fix #27805

[github-actions]

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[cfriedt]

LGTM - a great follow up commit or PR would be to list POSIX samples in the os services / portability / POSIX doc area.

Would be happy to re-approve if you wish to add that here, @dougwfoster ?

[kartben]

Thanks!
Additional note: line wrapping is a bit inconsistent in the two proposed files. I realize this might be due to copy-pasting from the other POSIX sample README, but it would make sense to adjust to have consistent 100-character long lines.

[kartben]

do you want to add the "For comparison, to build directly for your host OS if it is POSIX compliant (for ex. Linux):" ... thing here too? It's actually quite a nice thing to mention.

[dougwfoster]

I noticed the uname sample does not have a Makefile.host file. I tried adding one but ran into build errors due to the include files of the sample. I decided not to add a Makefile.host for the uname sample

[ycsin]

@dougwfoster this now can be done since #67648 is merged

[kartben]

adding a reference to eventfd() doc would be welcome here, but not sure why there's none on opengroup webpage? @cfriedt might know

[cfriedt]

eventfd() is not yet part of POSIX. It just happens to be lumped in with POSIX in Zephyr because it's available on most POSIX systems, is mostly dependent & compatible already on existing POSIX APIs, etc.

I'm ok taking eventfd() under the POSIX API wing in Zephyr, in any case.

[dougwfoster]

LGTM - a great follow up commit or PR would be to list POSIX samples in the os services / portability / POSIX doc area.

Would be happy to re-approve if you wish to add that here, @dougwfoster ?

That's a good idea. I can add a POSIX Sample section there or list them in the POSIX Applications in Zephyr section.

[cfriedt]

@dougwfoster - I think the samples portion should probably be automatically built (as long as the .rst files are captured by the main sample rst)

From the os services / portability / POSIX page, maybe just a link back to the samples would be good?

@kartben could probably be more specific.

[kartben]

non blocking: kind of not ideal that this adds a new untracked file to the git repo, but I guess it was already like that before.

[cfriedt]

LGTM - the only slight inaccuracy is that events is not POSIX (yet), even though it is available on many POSIX operating systems.

Otherwise, I think maybe @kartben could potentially offer some style suggestions?

[github-actions]

Hi @dougwfoster!
Congratulations on getting your very first Zephyr pull request merged 🎉🥳. This is a fantastic achievement, and we're thrilled to have you as part of our community!

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