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

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

@@ -0,0 +1,15 @@
+# ArduinoJson - arduinojson.org
+# Copyright Benoit Blanchon 2014-2020
+# MIT License
+
+add_executable(ElementProxyTests
+	add.cpp
+	clear.cpp
+	compare.cpp
+	remove.cpp
+	set.cpp
+	size.cpp
+)
+
+target_link_libraries(ElementProxyTests catch)
+add_test(ElementProxy ElementProxyTests)