How to generate Test Coverage #198

I wanted to see where testing could be improved, so I thought it would be a good idea to see the test coverage for the project. I tried my hand at setting up test coverage in https://github.com/Eunovo/libmultiprocess/tree/make-test-coverage

The process to generate the test coverage is:

cmake -B build -DCMAKE_BUILD_TYPE=Coverage
cd build
make tests
cmake -DLCOV_OPTS="--ignore-errors mismatch"  -P Coverage.cmake

The .gcno files are generated, but the .gcda files are not generated, so the process fails to complete.
I'm not sure why the gcda files are not being generated. I can see gcov symbols when I do nm ./test/mptest | grep gcov, but it doesn't work.