…istered step

Before:
```
thread 'main' panicked at 'error: no rules matched invalid', src/bootstrap/builder.rs:287:17
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```

After:
```
error: no `check` rules matched 'invalid'
help: run `x.py check --help --verbose` to show a list of available paths
note: if you are adding a new Step to bootstrap itself, make sure you register it with `describe!`
```

Bootstrap currently provides `-Zunstable-options` for OpenBSD when using
split debuginfo - this commit provides it for all BSD targets.

Signed-off-by: David Wood <[email protected]>

https://github.com/rust-lang/rust/blob/master/src/librustc_session/lint/builtin.rs
returns page not found.

The following is the background of the move.
First rust-lang#74862 moves from src/librustc_session/lint/builtin.rs
to compiler/rustc_session/src/lint/builtin.rs
Then rust-lang@23018a5 moves from compiler/rustc_session/src/lint/builtin.rs
to compiler/rustc_lint_defs/src/builtin.rs

So, the current correct link is https://github.com/rust-lang/rust/blob/master/compiler/rustc_lint_defs/src/builtin.rs

This PR fixes a broken link on the following page:
https://doc.rust-lang.org/beta/unstable-book/language-features/plugin.html

…=Mark-Simulacrum

[bootstrap] Give a better error when trying to run a path with no registered step

Before:
```
thread 'main' panicked at 'error: no rules matched invalid', src/bootstrap/builder.rs:287:17
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
```

After:
```
error: no `check` rules matched 'invalid'
help: run `x.py check --help --verbose` to show a list of available paths
note: if you are adding a new Step to bootstrap itself, make sure you register it with `describe!`
```

… r=Mark-Simulacrum

update `jemallocator` example to use 2018 edition import syntax

Fix an ICE on rust-lang#96738

In the block we don't know if the method actually exists thus `expect_local` panics.
Fixes rust-lang#96738
Fixes rust-lang#96583

…-bsd, r=Mark-Simulacrum

bootstrap: bsd platform flags for split debuginfo

Addresses rust-lang#96597 (comment).

Bootstrap currently provides `-Zunstable-options` for OpenBSD when using split debuginfo - this commit provides it for all BSD targets.

We should probably work out a better way of handling the stability of the split debuginfo flag - all options for the flag are unstable but one of them is the default for each platform already.

cc `@m-ou-se`
r? `@Mark-Simulacrum`

…-take-2, r=petrochenkov

Remove closures on `expect_local` to apply `#[track_caller]`

Pointed out in rust-lang#96747 (comment)
Didn't change `expect_non_local` as I'm not sure if it's also the case.
r? ``@petrochenkov``

…nstable_book, r=ehuss

Fix an incorrect link in The Unstable Book

https://github.com/rust-lang/rust/blob/master/src/librustc_session/lint/builtin.rs returns page not found.

The following is the background of the move.
First rust-lang#74862 moves from src/librustc_session/lint/builtin.rs to compiler/rustc_session/src/lint/builtin.rs.
Then rust-lang@23018a5 moves from compiler/rustc_session/src/lint/builtin.rs to compiler/rustc_lint_defs/src/builtin.rs.

So, the current correct link is https://github.com/rust-lang/rust/blob/master/compiler/rustc_lint_defs/src/builtin.rs.

This PR fixes a broken link on the following page:
https://doc.rust-lang.org/beta/unstable-book/language-features/plugin.html

…er-errors

Link to correct issue in issue-95034 known-bug

fix a typo is issue number: 94034 -> 95034

…=compiler-errors

Add regression test for rust-lang#96319