Update pidfd constants and types (Linux 6.9-6.15)

[rusty-snake]

Description

Add pidfd constants for thread targeting pidfds.

Sources

https://github.com/torvalds/linux/blob/3bde70a2c82712f05c7220b8b94fc2cbdf7fbfe0/include/uapi/linux/pidfd.h#L10-L21

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 label +stable-nominated

[rustbot]

r? @tgross35

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[rusty-snake]

(rebase)

[rusty-snake]

No idea why CI is failing.

[tgross35]

One small request but LGTM as long as CI passes. I'm not sure why the Windows job failed, those have been a bit spurious recently.

Could you also squash please?

[tgross35]

Actually, why is this GNU only? Shouldn't it be available for musl and other libcs since it is uapi?

[rusty-snake]

Yeah, glibc does nothing special. It has a some userspace helper functions like pidfd_getpid and APIs like pidfd_spawn (posix_spawn with pidfd support).
I simply looked for PIDFD_NONBLOCK and added the rest next to it.

Will move it to linux_like.

[rusty-snake]

Moved to linux_like/linux/mod.rs