Test CMake Config script

[remia]

This PR is a follow up of #1397, adding a simple test of the generated script.

• A dummy single file project is built and run after main library has been tested,
• Currently only enabled on shared build, it seems static build would be harder to test and require the client project to import the correct dependencies,
• Build is done in source to avoid some inconsistency in GitHub Action while changing directory within a single job (I had some issues in Windows),
• Added cxx_std_11 public compiler feature on the core library based on @hodoulp suggestion.

On a related note, I added an explicit warning ignore in the client project, the already known C4275. I wonder if we could do that from #pragma inside the source code (OCIO Exception class) to not impose that on the users.

[hodoulp]

On a related note, I added an explicit warning ignore in the client project, the already known C4275. I wonder if we could do that from #pragma inside the source code (OCIO Exception class) to not impose that on the users.

That's a good point. My answer is yes in OpenColorIO.h

[michdolan]

Great idea @remia !