avoid lambda to simplify source code

tests/dbc_decoder_test.cpp

@@ -118,7 +118,10 @@ int main() {
                                         10.0;
                 std::ostringstream actualText;
                 std::ostringstream expectedText;
-                std::visit([&actualText](auto raw) { actualText << raw; }, decoded.rawValue);
+                if (const auto *signedValue = std::get_if<std::int64_t>(&decoded.rawValue))
+                    actualText << *signedValue;
+                else
+                    actualText << std::get<std::uint64_t>(decoded.rawValue);
                 if (type == ValueType::Unsigned)
                     expectedText << bits;
                 else