FBE build fails on Windows using MQTT

[m-meingast]

@gravemalte

This is a successor to #27. After removing the OPC UA dependencies from the default.txt configuration, an issue with a SSL socket related to MQTT occured.

CMakeOutput.log
native-toolchain.log

In the end, having removed the OPC UA and the MQTT dependencies, at least the Forte compiled successfully.

[gravemalte]

This is about linking libpaho-mqtt with libreSSL.
I know that paho.mqtt.c features a CMake option for building explicitly with libreSSL see: https://github.com/eclipse-paho/paho.mqtt.c/blob/2150ba29d9df24ad1733c460eb099f292af84ee5/CMakeLists.txt#L56

I'm not sure if the linker is not able to locate the libreSSL .a (because of the CMake option) or the linking flag is somehow missing (or both?)

Currently, the paho receipt features the PAHO_WITH_SSL option see: https://github.com/eclipse-4diac/4diac-fbe/blob/release/dependencies/recipes/paho.mqtt.c/build.cmake#L17

[jwalt]

Thanks for the report. That is a bug in the build recipe for 4diac forte. MQTT depends on libssl, which happened to be pulled in by OPC UA. A fix is in the pipeline.