Wrong unpacked structure for epoll_event on qemu-or1k (openrisc)
Description of problem:
When using cmake automoc, the process will infinite loop waiting for epoll_events.
Steps to reproduce:
1. Try to compile cmake with qt5 support
2. The build process will freeze when "Automatic MOC" is invoked
Additional information:
The problem is that or1k has a "packed" epoll_event structure, so it should be also packed in target_epoll_event structure.
Following the (very trivial) patch:
```
--- qemu-20230327/linux-user/syscall_defs.h.orig	2023-03-27 15:41:42.000000000 +0200
+++ qemu-20230327/linux-user/syscall_defs.h	2023-06-30 17:29:39.034322213 +0200
@@ -2714,7 +2709,7 @@ 
 #define FUTEX_CMD_MASK          ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME)
 
 #ifdef CONFIG_EPOLL
-#if defined(TARGET_X86_64)
+#if defined(TARGET_X86_64) || defined(TARGET_OPENRISC)
 #define TARGET_EPOLL_PACKED QEMU_PACKED
 #else
 #define TARGET_EPOLL_PACKED
```