Fixed error expected unqualified-id on GCC 11 (fixes #1622)

extras/tests/Cpp20/CMakeLists.txt

@@ -0,0 +1,29 @@
+# ArduinoJson - https://arduinojson.org
+# Copyright Benoit Blanchon 2014-2021
+# MIT License
+
+if(MSVC_VERSION LESS 1910)
+	return()
+endif()
+
+if(CMAKE_CXX_COMPILER_ID MATCHES "Clang" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 10)
+	return()
+endif()
+
+if(CMAKE_CXX_COMPILER_ID STREQUAL "GNU" AND CMAKE_CXX_COMPILER_VERSION VERSION_LESS 10)
+	return()
+endif()
+
+set(CMAKE_CXX_STANDARD 20)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+
+add_executable(Cpp20Tests
+	smoke_test.cpp
+)
+
+add_test(Cpp20 Cpp20Tests)
+
+set_tests_properties(Cpp20
+	PROPERTIES
+		LABELS 		"Catch"
+)