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;