This reverts commit 7cae9e8.

Clippy does its own runtime detection of the sysroot, which was
incorrect in this case (it used the beta sysroot). This overrides the
sysroot to use `stage0-sysroot` instead.

- Get `x.py clippy` to work on nightly
- Give a nice error message if nightly clippy isn't installed

Not 100% sure this will _always_ work, but it works currently.

This undocumented feature allows you to typo 'a' as '1'.

Changes from 68965 extended the kind of instances that are being
inlined. For some of those, the `instance_mir` returns a MIR body that
is already expressed in terms of the types found in substitution array,
and doesn't need further substitution.

Use `substs_for_mir_body` to take that into account.

…ntax

This also adds a note about missing stack probes support, per the
discussion on RFC 2959.

Previously, trying to allow this would give another error!

```
warning: unknown lint: `private_intra_doc_links`
 --> private.rs:1:10
  |
1 | #![allow(private_intra_doc_links)]
  |          ^^^^^^^^^^^^^^^^^^^^^^^ help: did you mean: `broken_intra_doc_links`
  |
  = note: `#[warn(unknown_lints)]` on by default

warning: public documentation for `DocMe` links to private item `DontDocMe`
 --> private.rs:2:11
  |
2 | /// docs [DontDocMe]
  |           ^^^^^^^^^ this item is private
  |
  = note: `#[warn(private_intra_doc_links)]` on by default
  = note: this link will resolve properly if you pass `--document-private-items`
```

This is really starting to get out of hand. Rustdoc should instead allow
all lints in the rustdoc lint group.

This fixes ongoing issues where x.py will detect the wrong host triple
between MSVC and GNU.

- Add line to changelog

Here's the error for rustdoc:

```
Checking rustdoc artifacts (x86_64-unknown-linux-gnu -> x86_64-unknown-linux-gnu)
error: no library targets found in package `rustdoc-tool`
```

`#![deny(unsafe_op_in_unsafe_fn)]` in sys/hermit

Partial fix of rust-lang#73904.

This encloses ``unsafe`` operations in ``unsafe fn`` in ``sys/hermit``.
Some unsafe blocks are not well documented because some system-based functions lack documents.

…acrum

Fix `x.py clippy`

I don't think this ever worked.

Fixes rust-lang#77309. `--fix` support is a work in progress, but works for a very small subset of `libtest`.

This works by using the host `cargo-clippy` driver; it does not use `stage0.txt` at all. To mitigate confusion from this, it gives an error if you don't have `rustc +nightly` as the default rustc in `$PATH`. Additionally, it means that bootstrap can't set `RUSTC`; this makes it no longer possible for clippy to detect the sysroot itself. Instead, bootstrap passes the sysroot to cargo.

r? `@ghost`

…, r=jyn514,ollie27

Add non_autolinks lint

Part of rust-lang#77501.

r? `@jyn514`

Recognize `private_intra_doc_links` as a lint

Previously, trying to allow this would give another error!

```
warning: unknown lint: `private_intra_doc_links`
 --> private.rs:1:10
  |
1 | #![allow(private_intra_doc_links)]
  |          ^^^^^^^^^^^^^^^^^^^^^^^ help: did you mean: `broken_intra_doc_links`
  |
  = note: `#[warn(unknown_lints)]` on by default

warning: public documentation for `DocMe` links to private item `DontDocMe`
 --> private.rs:2:11
  |
2 | /// docs [DontDocMe]
  |           ^^^^^^^^^ this item is private
  |
  = note: `#[warn(private_intra_doc_links)]` on by default
  = note: this link will resolve properly if you pass `--document-private-items`
```

Fixes the issue found in rust-lang#77249 (comment).

r? `@Manishearth`

Does anyone know why this additional step is necessary? It seems weird this has to be declared in 3 different places.

…crum

Promote aarch64-unknown-linux-gnu to Tier 1

This PR promotes the `aarch64-unknown-linux-gnu` target to Tier 1, as proposed by [RFC 2959]:

* The `aarch64-gnu` CI job is moved from `auto-fallible` to `auto`.
* The platform support documentation is updated, uplifting the target to Tiert 1 with a note about missing stack probes support.
* Building the documentation is enabled for the target, as we produce the `rust-docs` component for all Tier 1 platforms.

[RFC 2959]: rust-lang/rfcs#2959

… r=Mark-Simulacrum

BTreeMap: stop mistaking node for an orderly place

A second mistake in rust-lang#77612 was to ignore the node module's rightful comment "this module doesn't care whether the entries are sorted". And there's a much simpler way to visit the keys in order, if you check this separately from a single pass checking everything.

r? `@Mark-Simulacrum`

…crum

fix some incorrect aliasing in the BTree

This line is wrong:
```
ptr::copy(slice.as_ptr().add(idx), slice.as_mut_ptr().add(idx + 1), slice.len() - idx);
```
When `slice.as_mut_ptr()` is called, that creates a mutable reference to the entire slice, which invalidates the raw pointer previously returned by `slice.as_ptr()`. (Miri currently misses this because raw pointers are not tracked properly.)

Cc `@ssomers`

…ulacrum

Infer the default host target from the host toolchain if possible

- `beta-x86_64-unknown-linux-gnu` has beta stripped
- `rustc2` is ignored

This fixes ongoing issues where x.py will detect the wrong host triple
between MSVC and GNU.

I don't think this will break anyone's workflow - I'd be very surprised if you a) had no `[build]` section in `config.toml`, b) had rustc installed, and c) expected the default target to be something other than the default target used by `rustc`. But I could be wrong - I'm happy to hear user stories :)

Fixes rust-lang#78150.

r? `@Mark-Simulacrum`
cc `@Lokathor`

Allow using 1/2/3/4 for `x.py setup` options

This undocumented feature allows you to typo 'a' as '1'.

r? `@Mark-Simulacrum`
cc `@Lokathor`

…imulacrum

BTreeMap: document a curious assumption in test cases

r? `@Mark-Simulacrum`

… r=oli-obk

inliner: Use substs_for_mir_body

Changes from 68965 extended the kind of instances that are being
inlined. For some of those, the `instance_mir` returns a MIR body that
is already expressed in terms of the types found in substitution array,
and doesn't need further substitution.

Use `substs_for_mir_body` to take that into account.

Resolves rust-lang#78529.
Resolves rust-lang#78560.