Auto merge of #134907 - Kobzol:rustc-dev-guide-josh, r=ehuss

Turn rustc-dev-guide into a Josh subtree

Discussed on [Zulip](https://rust-lang.zulipchat.com/#narrow/channel/196385-t-compiler.2Fwg-rustc-dev-guide/topic/a.20move.20to.20main.20repo.20.28rust-lang.2Frust.29).

Accompanying rustc-dev-guide PR: https://github.com/rust-lang/rustc-dev-guide/pull/2183

I didn't create a bootstrap step for rustc-dev-guide yet, because the rustc-dev-guide version that we currently use in this repo doesn't have linkcheck enabled and that fails tests.

The subtree starts with commit [ad93c5f1c49f2aeb45f7a4954017b1e607df9f5e](ad93c5f1c4).

What I did:
```
export DIR=src/doc/rustc-dev-guide

# Remove submodule
git submodule status ${DIR}
git submodule deinit ${DIR}
git rm -r --cached ${DIR}
rm -rf ${DIR}
# Remove rustc-dev-guide from .gitmodules
git commit -m"Removed `${DIR}` submodule"

# Import history with josh
git fetch https://github.com/rust-lang/rustc-dev-guide ad93c5f1c49f2aeb45f7a4954017b1e607df9f5e
josh-filter ':prefix=src/doc/rustc-dev-guide' FETCH_HEAD
git merge --allow-unrelated FILTERED_HEAD

# A few follow-up cleanup commits
```

r? ehuss

src/bootstrap/src/core/build_steps/doc.rs

@@ -63,7 +63,7 @@ macro_rules! book {
 }
 
 // NOTE: When adding a book here, make sure to ALSO build the book by
-// adding a build step in `src/bootstrap/builder.rs`!
+// adding a build step in `src/bootstrap/code/builder/mod.rs`!
 // NOTE: Make sure to add the corresponding submodule when adding a new book.
 // FIXME: Make checking for a submodule automatic somehow (maybe by having a list of all submodules
 // and checking against it?).

src/bootstrap/src/core/build_steps/test.rs

@@ -2525,35 +2525,6 @@ fn markdown_test(builder: &Builder<'_>, compiler: Compiler, markdown: &Path) ->
     }
 }
 
-#[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct RustcGuide;
-
-impl Step for RustcGuide {
-    type Output = ();
-    const DEFAULT: bool = false;
-    const ONLY_HOSTS: bool = true;
-
-    fn should_run(run: ShouldRun<'_>) -> ShouldRun<'_> {
-        run.path("src/doc/rustc-dev-guide")
-    }
-
-    fn make_run(run: RunConfig<'_>) {
-        run.builder.ensure(RustcGuide);
-    }
-
-    fn run(self, builder: &Builder<'_>) {
-        let relative_path = "src/doc/rustc-dev-guide";
-        builder.require_submodule(relative_path, None);
-
-        let src = builder.src.join(relative_path);
-        let mut rustbook_cmd = builder.tool_cmd(Tool::Rustbook).delay_failure();
-        rustbook_cmd.arg("linkcheck").arg(&src);
-        let toolstate =
-            if rustbook_cmd.run(builder) { ToolState::TestPass } else { ToolState::TestFail };
-        builder.save_toolstate("rustc-dev-guide", toolstate);
-    }
-}
-
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct CrateLibrustc {
     compiler: Compiler,

src/bootstrap/src/core/build_steps/toolstate.rs

@@ -76,10 +76,7 @@ static STABLE_TOOLS: &[(&str, &str)] = &[
 // We do require that we checked whether they build or not on the tools builder,
 // though, as otherwise we will be unable to file an issue if they start
 // failing.
-static NIGHTLY_TOOLS: &[(&str, &str)] = &[
-    ("embedded-book", "src/doc/embedded-book"),
-    // ("rustc-dev-guide", "src/doc/rustc-dev-guide"),
-];
+static NIGHTLY_TOOLS: &[(&str, &str)] = &[("embedded-book", "src/doc/embedded-book")];
 
 fn print_error(tool: &str, submodule: &str) {
     eprintln!();

src/bootstrap/src/core/builder/mod.rs

@@ -951,7 +951,6 @@ impl<'a> Builder<'a> {
                 test::UnstableBook,
                 test::RustcBook,
                 test::LintDocs,
-                test::RustcGuide,
                 test::EmbeddedBook,
                 test::EditionGuide,
                 test::Rustfmt,