Don't skip asserts in unit test release builds

[rogernelson]

Fixes #1235

Summarize your change.

This branch undefines NDEBUG when using unit tests. This is to ensure the asserts used in assertEqual and assertNotEqual, etc fail the test even in release builds. Since this file is only included by the unit tests it won't have any impact outside of that scope.

Reference associated tests.

test_clip.cpp and test_opentime.cpp

[rogernelson]

I can't modify the list of reviewers, but I'd like to request that @darbyjohnston review this.

[darbyjohnston]

Seems like a reasonable change, I guess I had assumed the tests would always be run in Debug mode.

[meshula]

From a philosophical standpoint, tests need to be run in Release, otherwise they don't reflect the common deployment situation. It's good to also run in Debug, although one sees that less often in the wild.

[meshula]

Thanks for the catch! Over time we should move away from cstd assertions, and towards a framework of some sort. If anyone is thinking about that, lighter is better, speaking for myself, I'd prefer a homegrown framework, or at least a framework that is not larger than OTIO itself ;)