Add —output-on-failure to CI unit test command

Currently we use the following command to run the tests in the CI:
```
cmake —build build —target test
```

It would be better to use the output on failure so that the CI logs show more information when a failure occurs.
The above command could be replaced with:
```
ctest —test-dir build —output-on-failure
```

(The double hyphen seems to have been consumed into long dash.)