Fix joining non-Started threads from blocking main thread

core/thread/thread_unix.odin

@@ -36,6 +36,10 @@ _create :: proc(procedure: Thread_Proc, priority: Thread_Priority) -> ^Thread {
 			sync.wait(&t.cond, &t.mutex)
 		}
 
+		if .Joined in t.flags {
+			return nil
+		}
+
 		when ODIN_OS != .Darwin {
 			// Enable thread's cancelability.
 			if can_set_thread_cancel_state {
@@ -143,6 +147,11 @@ _join :: proc(t: ^Thread) {
 	if res, ok := CAS(&t.flags, unjoined, joined); res == joined && !ok {
 		return
 	}
+	// Prevent non-started threads from blocking main thread with initial wait
+	// condition.
+	if .Started not_in unjoined {
+		_start(t)
+	}
 	unix.pthread_join(t.unix_thread, nil)
 }