feat(std): emulate flock for solaris via fcntl

[weihanglo]

Upstream Solaris flock emulation to libstd from cargo.

This is borrowed from
https://github.com/rust-lang/cargo/blob/3b379fcc541b39321a7758552d37e5e0cc4277b9/src/cargo/util/flock.rs#L502-L536 which was implemented by an Oracle employee.
The code has been in cargo since 2022-12.

Python's fcntl.flock emulates like this as well: https://github.com/python/cpython/blob/c919d02edecfe9d75fe374756fb8aa1db8d95f55/Modules/fcntlmodule.c#L337-L400

We did the same thing in

rust/compiler/rustc_data_structures/src/flock/unix.rs

Lines 13 to 39 in 0d0f4ea

	let file = OpenOptions::new()
	.read(true)
	.write(true)
	.create(create)
	.mode(libc::S_IRWXU as u32)
	.open(p)?;
	let lock_type = if exclusive { libc::F_WRLCK } else { libc::F_RDLCK };
	let mut flock: libc::flock = unsafe { mem::zeroed() };
	#[cfg(not(all(target_os = "hurd", target_arch = "x86")))]
	{
	flock.l_type = lock_type as libc::c_short;
	flock.l_whence = libc::SEEK_SET as libc::c_short;
	}
	#[cfg(all(target_os = "hurd", target_arch = "x86"))]
	{
	flock.l_type = lock_type as libc::c_int;
	flock.l_whence = libc::SEEK_SET as libc::c_int;
	}
	flock.l_start = 0;
	flock.l_len = 0;
	let cmd = if wait { libc::F_SETLKW } else { libc::F_SETLK };
	let ret = unsafe { libc::fcntl(file.as_raw_fd(), cmd, &flock) };
	if ret == -1 { Err(io::Error::last_os_error()) } else { Ok(Lock { file }) }
	}

However, should we just always falls back to fcntl for all Unix, instead of "unsupported"?

try-job: *-solaris

[rustbot]

r? @Mark-Simulacrum

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[weihanglo]

cc @psumbera

[weihanglo]

@bors try

[rust-bors]

☀️ Try build successful (CI)
Build commit: bd77cf6 (bd77cf6012347fd5f68759320ff8e2d5dd2cf6a4, parent: 76863e340416e7f21955bdaf0ae9728eb51f5671)

[weihanglo]

@rustbot ready

This should be good for review :)

[Mark-Simulacrum]

@bors r+

[bors]

📌 Commit 01edb24 has been approved by Mark-Simulacrum

It is now in the queue for this repository.