Merge branch 'jc/cmake-unit-test-updates'

CMake adjustments for recent changes around unit tests.

* jc/cmake-unit-test-updates:
  cmake: generalize the handling of the `UNIT_TEST_OBJS` list
  cmake: stop looking for `REFTABLE_TEST_OBJS` in the Makefile
  cmake: rename clar-related variables to avoid confusion