Rollup merge of rust-lang#140210 - Berrysoft:cygwin-timedwait, r=joboet

Work around cygwin issue on condvar timeout

This workaround *just works*... Actually I don't quite understand why does it work in such way. With a simple test on Cygwin, it seems that the maximum value of `tv_sec` could be 12899331056917, while the maximum value of `tv_nsec` should be a value floating around 464600000. A larger `timespec` could block the syscall forever.

r? `@joboet`

Author: matthiaskrgr

library/std/src/sys/pal/unix/sync/condvar.rs

@@ -64,7 +64,10 @@ impl Condvar {
         // https://gist.github.com/stepancheg/198db4623a20aad2ad7cddb8fda4a63c
         //
         // To work around this issue, the timeout is clamped to 1000 years.
-        #[cfg(target_vendor = "apple")]
+        //
+        // Cygwin implementation is based on NT API and a super large timeout
+        // makes the syscall block forever.
+        #[cfg(any(target_vendor = "apple", target_os = "cygwin"))]
         let dur = Duration::min(dur, Duration::from_secs(1000 * 365 * 86400));
 
         let timeout = Timespec::now(Self::CLOCK).checked_add_duration(&dur);