CMake build scripts don't add dependency on supporting files when running unit tests

[josyoun]

Right now, there's no dependency on the supporting files for the unit tests. That means when supporting files for the unit test are modified, we don't get the updates to the unit tests. Two places where this occurs are in the perceptron and computation_caching examples. The short fix is to delete these directories in the build folder, but it'd be nice do do this correctly.