Make sure to rebuild rustdoc if src/rustdoc-json-types is changed

[jieyouxu]

I think rustdoc-json-types was more recently split out, so this download-rustc logic became outdated as it wasn't tracked. This PR adds src/rustdoc-json-types to be tracked for difference versus upstream, so that we properly rebuild rustdoc if it has changes versus upstream.

Fixes #142738.

Local testing

This is not so easy to test locally because it requires download-rustc. To test this, you need to:

1. Disable download-rustc inhibition from bootstrap changes versus upstream, by including :!src/bootstrap in

   rust/src/bootstrap/src/core/config/config.rs

   Lines 67 to 74 in 255aa22

   	pub const RUSTC_IF_UNCHANGED_ALLOWED_PATHS: &[&str] = &[
   	":!library",
   	":!src/tools",
   	":!src/librustdoc",
   	":!src/rustdoc-json-types",
   	":!tests",
   	":!triagebot.toml",
   	];

   .
2. Then, use a config like profile = "tools" which by default uses download-rustc = "if-unchanged".
3. Run ./x test tests/rustdoc-json one time, to "prime" initial build caches.
4. Change the FORMAT_VERSION in src/rustdoc-json-types, i.e.

   diff --git a/src/rustdoc-json-types/lib.rs b/src/rustdoc-json-types/lib.rs
   index 1f93895ae07..72a3720c7b4 100644
   --- a/src/rustdoc-json-types/lib.rs
   +++ b/src/rustdoc-json-types/lib.rs
   @@ -38,7 +38,7 @@
    // are deliberately not in a doc comment, because they need not be in public docs.)
    //
    // Latest feature: Pretty printing of inline attributes changed
   -pub const FORMAT_VERSION: u32 = 48;
   +pub const FORMAT_VERSION: u32 = 666;

5. Observe that without this patch, rustdoc-json tests fail because FORMAT_VERSION mismatch. Observe that with this patch, rustdoc gets properly rebuilt and rustdoc-json tests pass.

cc @aDotInTheVoid

r? Kobzol

[aDotInTheVoid]

Thanks ❤️!

I think rustdoc-json-types was more recently split out

It's been around for ages (#81287), I think this was hidden for so longer because modifying rustdoc-json-types without also modifying librustdoc doesn't make much sense.

[Kobzol]

@bors r+ rollup

[bors]

📌 Commit fca6e81 has been approved by Kobzol

It is now in the queue for this repository.