running a single test

Hey!

I'm trying to run a single test via:

```
../../../../../_build/default/src/lib/pickles/.pickles.inline-tests/inline_test_runner_pickles.exe inline-test-runner Pickles -only-test pickles.ml:981
```

but I'm getting

```
ppx_inline_test error: the following -only-test flags matched nothing: pickles.ml:981.
```

whereas the file indeed exists at my path. I'm a bit confused on how to use that option

Reproduce the command shown against the inline_test_runner_pickles.exe executable and the pickles.ml:981 selector. Read the -only-test handling and matching behavior, then verify the result against the inline test at that location. Done means the selector behavior is corrected or its required syntax is clearly documented.

Written by the indexing model from the issue text.