chore: exit in ONCE()

Author: dy-tea

include/once.h

@@ -4,8 +4,10 @@
 #define ONCE() \
   do { \
     static int _called_once_flag_##__LINE__ = 0; \
-    if (_called_once_flag_##__LINE__) \
+    if (_called_once_flag_##__LINE__) { \
      	wlr_log(WLR_ERROR, "Function %s called more than once", __func__); \
+      exit(1); \
+    } \
     _called_once_flag_##__LINE__ = 1; \
   } while(0)
 #else