Build instructions should read "# or"

@alandefreitas , your reply was detailed, and at the moment I am not following the thread. Which leads through mrdocs, antora, command-line options, and so on. That's ok. How about this:

Pull request 283 only fixes the macOS issue (which I believe it does.) Done.
In another PR, when you have a chance, you could update the README. Considering these points:

- "We need your `# or` comment."
- The README mentions multiple output dirs. `Open file:///home/user/path/to/antora/build/develop/doc` and `Open file:///home/user/path/to/antora/build/doc`. If switching to `or` it would only be one directory?
- A suggestion that the output location is described this way. (not required).

```
/home/user/website-v2-docs/build
```

or

```
/home/user/website-v2-docs/build (or wherever you have checked out the repository)
```
- anything else

_Originally posted by @sdarwin in https://github.com/boostorg/website-v2-docs/issues/283#issuecomment-2284357049_