Enable simulation interrupt mode support

test/exit_group/main.c

@@ -18,14 +18,7 @@
 
 // Type 1: a busy loop thread
 static void *busyloop_thread_func(void *_) {
-// FIXME: Disable support for interrupting user code in simulation mode becase
-// the interrupt signal is not handled well.
-#ifdef SGX_MODE_SIM
-    printf("WARNING: Skip busyloop_thread_func case as we do not support "
-           "interrupting user code in SGX simulation mode\n");
-#else
     while (1) {  }
-#endif
     return NULL;
 }