use local library source instead to correct some black-box issue for aliyuniot

lib/ArduinoJson/extras/tests/JsonSerializer/CMakeLists.txt

@@ -0,0 +1,18 @@
+# ArduinoJson - arduinojson.org
+# Copyright Benoit Blanchon 2014-2020
+# MIT License
+
+add_executable(JsonSerializerTests
+	CustomWriter.cpp
+	JsonArray.cpp
+	JsonArrayPretty.cpp
+	JsonObject.cpp
+	JsonObjectPretty.cpp
+	JsonVariant.cpp
+	misc.cpp
+	std_stream.cpp
+	std_string.cpp
+)
+
+target_link_libraries(JsonSerializerTests catch)
+add_test(JsonSerializer JsonSerializerTests)