Fix cpplint warning in util/safe_arith.cpp

src/util/safe_arith.cpp

@@ -9,7 +9,7 @@ Author: Leonardo de Moura
 
 namespace lean {
 void check_int_overflow(long long n) {
-    static_assert(sizeof(long long) > sizeof(int),
+    static_assert(sizeof(n) > sizeof(int), // NOLINT
                   "sizeof(long long) is not bigger than sizeof(int).");
     if (n < std::numeric_limits<int>::min())
         throw exception("integer underflow");