FWIU this is a use case that we expect to be working after #399: I have only fastrtps installed, and I want to use the opensplice+fastrtps combo archive, but am unable to unless I install opensplice.

$ ./lib/demo_nodes_cpp/talker
dyld: Library not loaded: @rpath/libcmxml.dylib
  Referenced from: /Users/dhood/Downloads/ros2-ardent-opsl-fastrtps/lib/libexample_interfaces__rosidl_typesupport_opensplice_c.dylib
  Reason: image not found
Trace/BPT trap: 5

I had previously had an older version of opensplice installed but have removed it.

@dirk-thomas is this supposed to be supported?