Add helper functions for creating OS specific library names

[wjwwood]

This won't always work (depending on how people build their plugin libraries), but it should allow for less code in the default case.

[dirk-thomas]

+1

[dirk-thomas]

Locally the test fails for me when being build in a ROS 2 workspace with the following error:

/home/dthomas/ros/ros2/ws_ros2/src/ros2/class_loader/test/fviz_case_study/fviz_test.cpp:17
Failed
ClassLoaderException: Could not load library (Poco exception = libclass_loader_Test_FvizDefaultPlugind.so: cannot open shared object file: No such file or directory)

[dirk-thomas]

But the utest also fails for me in that case which might be related.

[wjwwood]

@dirk-thomas That's strange, are you sure that you had this branch checkout at that point? The CI job passed: https://travis-ci.org/ros/class_loader/jobs/87561847

Do you see anything obvious that I might be doing wrong/differently from your local system that might cause that? https://github.com/ros/class_loader/blob/ros2/.travis.yml

I'll try it in my local vm.

[wjwwood]

I just tested this on my Trusty VM, but I cannot reproduce it. Can you try again?

[dirk-thomas]

I reran the tests in my local workspace and the tests still fail with the same error.

[wjwwood]

I believe it's because you're building as Debug, so it is appending d.so instead of .so. This is something that Poco does, which I think it incorrect. I'll open a ticket to track the issue and look into the appropriate solution: #31