fix(printf): fix 'expression is constant' warning

printf.c

@@ -623,7 +623,8 @@ static int _vsnprintf(out_fct_type out, char* buffer, const size_t maxlen, const
         width = sizeof(void*) * 2U;
         flags |= FLAGS_ZEROPAD | FLAGS_UPPERCASE;
 #if defined(PRINTF_SUPPORT_LONG_LONG)
-        if (sizeof(uintptr_t) == sizeof(long long)) {
+        const bool is_ll = sizeof(uintptr_t) == sizeof(long long);
+        if (is_ll) {
           idx = _ntoa_long_long(out, buffer, idx, maxlen, (uintptr_t)va_arg(va, void*), false, 16U, precision, width, flags);
         }
         else {