XRCE multithreading not supported for this platform - FreeRTOS - wrong flag

[bjv-capra]

From micro-ROS/micro_ros_setup#312
I was trying to enable multithread support, however, I got

eProsima/Micro-XRCE-DDS-Client/src/c/profile/multithread/multithread.c:23:2: error: #error XRCE multithreading not supported for this platform.

By quickly skimming the code, it seems the wrong flag is used for FreeRTOS. I'm using FreeRTOS+TCP, on the base CMakeLists.txt, this sets UCLIENT_PLATFORM_FREERTOS_PLUS_TCP, on the other hand, https://github.com/eProsima/Micro-XRCE-DDS-Client/blob/foxy/src/c/profile/multithread/multithread.c#L13 expects to be PLATFORM_NAME_FREERTOS. As a workaround, I can set the flag on my colcon meta, but I think it's not the intended behavior.

[pablogs9]

Yes, this was the intended behavior because FreeRTOS does not have a common set of flags for checking when it is being used, so the user is in charge of defining PLATFORM_NAME_FREERTOS. The point is that UCLIENT_PLATFORM_FREERTOS_PLUS_TCP only refers to a TCP/UDP transport layer and FreeRTOS can be used with other transports.