Improve cmake duplicate component check

[gojimmypi]

A slight polish to the updates in #420

The PR modifies the CHECK_DUPLICATE_LIBRARIES CMake function to ensure false-positive duplicate library messages will not occur.

This is likely only a problem for me at this moment, due to these two lines.

        "${CMAKE_CURRENT_LIST_DIR}/managed_components/gojimmypi__my${KEYWORD}"
        "${CMAKE_CURRENT_LIST_DIR}/managed_components/${THIS_USER}__my${KEYWORD}"

Some other user may use the mywolfmqtt library and/or create their own mywolfmqtt component.

There's also an update in output message format to make it much more obvious when duplicate component directories are found.

This is as-published code in staging gojimmypi/mywolfmqtt 1.18.0-preview8b and wolfssl/wolfmqtt 1.18.0-preview8d