Relocate <spawn.h> functions to define them to dragonfly.

[jrmarino]

While here:

• Relocate mkostemp and mkostemps functions for same reason
• Update semver tests for DF spawn and mkostemp(s)

Description

This changeset exposes bindings for mkostemp, mkostemps, and the <spawn.h> functions on DragonFly.
It does this by moving freebsd-specific definitions in the generic freebsdlike mod.rs file.
These are required to build fish 4.0.0 (https://github.com/fish-shell/fish-shell)

Sources

FreeBSD

https://github.com/freebsd/freebsd-src/blob/e7c0cb720898fd36487c4e6b0aff52435084e6bf/include/spawn.h
https://github.com/freebsd/freebsd-src/blob/e7c0cb720898fd36487c4e6b0aff52435084e6bf/include/stdlib.h#L305-L307

DragonFly

https://raw.githubusercontent.com/DragonFlyBSD/DragonFlyBSD/refs/heads/master/include/spawn.h
https://raw.githubusercontent.com/DragonFlyBSD/DragonFlyBSD/refs/heads/master/include/stdlib.h

Checklist

• Relevant tests in libc-test/semver have been updated
• No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI

[rustbot]

r? @tgross35

rustbot has assigned @tgross35.
They will have a look at your PR within the next two weeks and either review your PR or reassign to another reviewer.

Use r? to explicitly pick a reviewer

[jrmarino]

replaces #4294

[tgross35]

LGTM after CI passes, please add permalinks to the actual headers in the PR description.

@rustbot label +stable-nominated

[jrmarino]

Okay, I updated the PR description with links to github mirror to the headers.
I'm worried about the nightly freebsd-13 x86_64 failure. I don't think my change caused it, but I am nowhere close to an expert.

[tgross35]

Oh does Dragonfly just use the FreeBSD headers? Thanks for the links, I updated them to permalinks so we have a reference if things change.

That job has been a bit flaky through Cirrus updates, looks like it passed with a rerun.

[jrmarino]

oh, sorry, that was a mistake, I'm not sure what I was thinking about those headers.. I will update again.

[jrmarino]

Okay, both FreeBSD and DragonFly header paths are provided now.

[tgross35]

Awesome, thank you. I updated these to permalinks as well (it's just an option under the triple dots when looking at a file on GH).