Fix unsupported std::sys::thread

Fixes building std for any platform with an unsupported thread
abstraction. This includes {aarch64,armv7,x86_64}-unknown-trusty and
riscv32im-risc0-zkvm-elf, which explicitly include the unsupported
module, and platforms with no PAL.

Bug fix for PR 145177 (std: move thread into sys).

Author: thaliaarchi

library/std/src/sys/pal/trusty/mod.rs

@@ -7,8 +7,6 @@ mod common;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
-#[path = "../unsupported/thread.rs"]
-pub mod thread;
 #[path = "../unsupported/time.rs"]
 pub mod time;
 

library/std/src/sys/pal/unsupported/mod.rs

@@ -2,7 +2,6 @@
 
 pub mod os;
 pub mod pipe;
-pub mod thread;
 pub mod time;
 
 mod common;

library/std/src/sys/pal/zkvm/mod.rs

@@ -14,8 +14,6 @@ pub mod abi;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
-#[path = "../unsupported/thread.rs"]
-pub mod thread;
 #[path = "../unsupported/time.rs"]
 pub mod time;
 

library/std/src/sys/process/unix/vxworks.rs

@@ -4,8 +4,7 @@ use libc::{self, RTP_ID, c_char, c_int};
 use super::common::*;
 use crate::io::{self, ErrorKind};
 use crate::num::NonZero;
-use crate::sys::cvt;
-use crate::sys::pal::thread;
+use crate::sys::{cvt, thread};
 use crate::{fmt, sys};
 
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