Add test for process exit initiated by thread

Author: surban

tests/ui/thread-local/spawned-thread-dtor.rs

@@ -0,0 +1,26 @@
+//! Ensure that TLS destructors run on a spawned thread that
+//! exits the process.
+//@ run-pass
+//@ needs-threads
+//@ check-run-results
+
+struct Foo;
+
+impl Drop for Foo {
+    fn drop(&mut self) {
+        println!("Foo dtor");
+    }
+}
+
+thread_local!(static FOO: Foo = Foo);
+
+fn main() {
+    std::thread::spawn(|| {
+        FOO.with(|_| {});
+        std::process::exit(0);
+    });
+
+    loop {
+        std::thread::park();
+    }
+}

tests/ui/thread-local/spawned-thread-dtor.rs.stdout

@@ -0,0 +1 @@
+Foo dtor