bootstrap: build bootstrap docs with in-tree rustdoc

[notriddle]

All of the docs need to be built with the same rustdoc. Otherwise, any change to the search index breaks everything, because the two rustdocs don't agree on the format.

Fixes #147142

[rustbot]

r? @Mark-Simulacrum

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[RalfJung]

Maybe have a comment somewhere emphasizing that everything needs to be documented with the same rustdoc?

[Kobzol]

That's not 100% true. For local usage, you can document them with whatever you want, you only need the same rustdoc when you dist everything together and ship it as a single docs directory.

[Kobzol]

Hmm, this is not the best solution, because ideally we would still allow documenting local stage0 stuff using stage0 rustdoc, but override the rustdoc being used for the actual doc dist steps. However, that would require a lot of non-trivial refactoring due to the way the dist doc steps are currently structured. And I assume that not many people actually run stage0 rustdoc on these tools locally, so it shouldn't hopefully be a usability regression.

So let's go forward with this, for now.

Please let's just add a small comment on top of these stage0 tool_doc invocations that says that they currently use tool_target in order to be documented with stage1+ rustdoc when we dist them. Then you can r=me.

r? @Kobzol

[GuillaumeGomez]

Is there anyone using stage 0 rustdoc to build docs?

[Mark-Simulacrum]

Is there some way for bootstrap or rustdoc to notice (perhaps in the dist artifacts?) that we used two different versions and bail out? Maybe when we produce the rustc and std doc components we could run such a check?

[notriddle]

Okay, I've added the comment.

@bors r=Kobzol

[bors]

📌 Commit ba13b6e has been approved by Kobzol

It is now in the queue for this repository.

[Kobzol]

Is there some way for bootstrap or rustdoc to notice (perhaps in the dist artifacts?) that we used two different versions and bail out? Maybe when we produce the rustc and std doc components we could run such a check?

I guess we'd have to add some metadata to the generated documentation and then check it in a post-dist test.

I think that the current bootstrap snapshot test is enough.