Fastfile: Run tests with BUILD_LIBRARY_FOR_DISTRIBUTION.

[byohay]

Solves #266

[ghost]

Is the intent here just to make sure that running tests with BUILD_LIBRARY_FOR_DISTRIBUTION doesn't break anything? I would have expected some kind of change in the project file or package spec as well.

[byohay]

To my understanding, if your clients don't intend to build JOSESwift separately you shouldn't enable library evolution (See here, under "When to enable library evolution support"). So if your clients wants to build it separately they should enable it themselves.
On another matter: Clients who pre-compile the library will use the archive command, but the current check runs the tests. Should I add another step that checks with the archive command? Or is it an overkill to add a step just for that?

[byohay]

@nathan-mohemian what are your thoughts on the matter?