embedded builds used to refer to undefined functions inside if(0) { }

gcc optimized this dead code away, and does not notice that functions
were undefined. Other compilers are more picky

sql/sql_acl.cc

@@ -6849,6 +6849,7 @@ bool check_routine_level_acl(THD *thd, const char *db, const char *name,
 #define initialized 0
 #define decrease_user_connections(X)        /* nothing */
 #define check_for_max_user_connections(X,Y)   0
+#define get_or_create_user_conn(A,B,C,D) 0
 #endif
 #endif
 #ifndef HAVE_OPENSSL