Change unit tests to run as post-build step.
Change unit tests to run as post-build step.

This is how it used to be in most of the old project files. The
CMake conversion required the tests to be run manually after the
build, either by running the binary directly or by calling CTest.
This commit removes the 'dependency' on CTest and restores the
old build process.

neilmacintosh/unittest-cpp,DavidLudwig/unittest-cpp,jasonhorsburgh/unittest-cpp,unittest-cpp/unittest-cpp,jasonhorsburgh/unittest-cpp,gleibson/unittest-cpp,grahamreeds/unittest-cpp,Microsoft/unittest-cpp,DavidLudwig/unittest-cpp,LocutusOfBorg/unittest-cpp,grahamreeds/unittest-cpp,unittest-cpp/unittest-cpp,Microsoft/unittest-cpp,grahamreeds/unittest-cpp,pjohnmeyer/unittest-cpp,LocutusOfBorg/unittest-cpp,lanurmi/unittest-cpp,gleibson/unittest-cpp,unittest-cpp/unittest-cpp,lanurmi/unittest-cpp,pjohnmeyer/unittest-cpp,neilmacintosh/unittest-cpp