building auto_index on macOS

In release-tools/build_docs, I am testing building the boost documentation for all libraries on Windows, Linux, MacOS.

The following libraries have a dependency on auto_index: math multiprecision pool type_traits vmd

I might be doing something wrong, but it seems that auto_index is not building on MacOS.

```
./b2 -q -d0 --build-dir=build --distdir=build/dist tools/quickbook tools/auto_index/build
```

The build completes without error and generates `quickbook`, but doesn't create the required file `build/dist/bin/auto_index`

- Could GitHub Actions CI tests be added to auto_index including macos-11,12,13 ?
- In the tests, check if the file build/dist/bin/auto_index is generated.

@pdimov may have been working on adding tests, the most recent commit: "attempt to get test dependencies to work".