CMake error CMP0002 when added multiple times

[alexmrtn]

Hi,

The top level CMakeLists.txt file is missing a guard when this project is recursively added in several places. As example, if a project uses both azure-iot-sdk-c and azure-event-hubs-c using the add_subdirectory cmake function, it triggers a CMP0002 error.

Can you add this lines of code as it is done for the umqtt to fix this ?

if (TARGET amqp)
    RETURN()
endif()

Thanks!