add test for detaching terminated thread on windows

Author: beepster4096

tests/pass/concurrency/windows_detach_terminated.rs

@@ -0,0 +1,21 @@
+//@only-target-windows: Uses win32 api functions
+// We are making scheduler assumptions here.
+//@compile-flags: -Zmiri-preemption-rate=0
+
+use std::os::windows::io::IntoRawHandle;
+use std::thread;
+
+extern "system" {
+    fn CloseHandle(handle: usize) -> i32;
+}
+
+fn main() {
+    let thread = thread::spawn(|| {}).into_raw_handle() as usize;
+
+    // this yield ensures that `thread` is terminated by this point
+    thread::yield_now();
+
+    unsafe {
+        assert_ne!(CloseHandle(thread), 0);
+    }
+}