Insta-stabilize the methods `is_ready` and `is_pending` of `Poll`.

Possible because of the recent stabilization of const control flow.

Also adds a test for these methods in a const context.

Part of rust-lang#76268

Due to the recent release of 1.47.0, this PR will be stabilized in 1.49.0 instead of 1.48.0.

This adds a binary called `x` in `src/tools/x`. All it does is check the
current directory and its ancestors for a file called `x.py`, and if it
finds one, runs it.

By installing x, you can easily `x.py` from any subdirectory.

It can be installed globally with `cargo install --path src/tools/x`

Also includes:
- Cell::into_inner
- RefCell::into_inner
- Atomic*::into_inner

Partially fix rust-lang#55002, deprecate in another release

Co-authored-by: Ashley Mannix <kodraus@hey.com>

Update stable version for stabilize_spin_loop

Co-authored-by: Joshua Nelson <joshua@yottadb.com>

Use better example for spinlock

As suggested by KodrAus

Remove renamed_spin_loop already available in master

Fix spin loop example

Includes:
- io::Cursor::new
- io::Cursor::get_ref
- io::Cursor::position
- io::empty
- io::repeat
- io::sink

Should hopefully fix rust-lang#78341 and rust-lang#78340.

Prior to this, setting the rustfmt configuration was ignored:

```
% mkdir example

% cd example

% ../configure --set build.rustfmt=/usr/bin/true

% ../x.py fmt
./x.py fmt is not supported on this channel
failed to run: /Users/shep/Projects/rust/example/build/bootstrap/debug/bootstrap fmt
Build completed unsuccessfully in 0:00:01
```

And after:

```
% ../x.py fmt
Build completed successfully in 0:00:11
```

The inlining integrator produces relatively verbose and uninteresting
logs.  Move them from a debug log level to a trace level, so that they
can be easily isolated from others.

fixed a typo and modified some line formatting justification while I'm here :)

Fixes rust-lang#78819

This extends the check for dereferences added in PR rust-lang#77324
to cover mutable borrows, as well as direct writes. If we're operating
on a dereference of a `const` item, we shouldn't be firing the lint.

…rAus

Stabilize hint::spin_loop

Partially fix rust-lang#55002, deprecate in another release

r? ``````@KodrAus``````

Stabilize `Poll::is_ready` and `is_pending` as const

Insta-stabilize the methods `is_ready` and `is_pending` of `std::task::Poll` as const, in the same way as [PR#76198](rust-lang#76198).

Possible because of the recent stabilization of const control flow.

Part of rust-lang#76225.

make concurrency helper more pleasant to read

…-size, r=jyn514

Remove FIXME comment in print_type_sizes ui test suite

## Overview
Helps with rust-lang#62277

> The type sizes are likely only printed when the actual layout is computed. For generic types, this only happens during codegen.

ref: https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/Codegen.20process.20question/near/215836807

Some tests like `multiple_types.rs` are passed even if using `check-pass`. But tests should be agnostic to when the actual layout is computed. The `build-pass` is intentionally used for them. I remove FIXME comments.

Use SOCK_CLOEXEC and accept4() on more platforms.

This PR enables the use of `SOCK_CLOEXEC` and `accept4` on more platforms.

-----

Android uses the linux kernel, so it should also support it.

DragonflyBSD introduced them in 4.4 (December 2015):
https://www.dragonflybsd.org/release44/

FreeBSD introduced them in 10.0 (January 2014):
https://wiki.freebsd.org/AtomicCloseOnExec

Illumos introduced them in a commit in April 2013, not sure when it was released. It is quite possible that is has always been in Illumos:
illumos/illumos-gate@5dbfd19
https://illumos.org/man/3socket/socket
https://illumos.org/man/3socket/accept4

NetBSD introduced them in 6.0 (Oktober 2012) and 8.0 (July 2018):
https://man.netbsd.org/NetBSD-6.0/socket.2
https://man.netbsd.org/NetBSD-8.0/accept.2

OpenBSD introduced them in 5.7 (May 2015):
https://man.openbsd.org/socket https://man.openbsd.org/accept

Add a tool to run `x.py` from any subdirectory

This adds a binary called `x` in `src/tools/x`. All it does is check the current directory and its ancestors for a file called `x.py`, and if it finds one, runs it.

By installing x, you can easily run `x.py` from any subdirectory, and only need to type `x`.

It can be installed with `cargo install --path src/tools/x`

This is a copy of a [binary I've been using myself when working on rust](https://github.com/casey/bootstrap), currently published to crates.io as `bootstrap`.

It could be changed to avoid indirecting through `x.py`, and instead call the bootstrap module directly. However, this seemed like the simplest thing possible, and won't break if the details of how the bootstrap module is invoked change.

…=Mark-Simulacrum

Fix run-make tests running when LLVM is disabled

The `--cc`, `--cxx`, `--cflags` and `--ar` flags were only passed to compiletest when `builder.config.llvm_enabled()` returned true. This is preventing me from running the tests on cg_clif.

…lnay

Constantify `UnsafeCell::into_inner` and related

Tracking issue: rust-lang#78729

This PR constantifies:
- `UnsafeCell::into_inner`
- `Cell::into_inner`
- `RefCell::into_inner`
- `Atomic*::into_inner`

r? `````@dtolnay`````

…lacrum

Bump Rustfmt and RLS

Should hopefully fix rust-lang#78341 and fix rust-lang#78340.

Correct unsigned equivalent of isize to be usize

See [rust-lang#74913 (comment)](rust-lang#74913 (comment)) for why this matters. Apparently it hasn't been used anywhere else, though CI will tell for sure.

Make some std::io functions `const`

Tracking issue: rust-lang#78812

Make the following functions `const`:
- `io::Cursor::new`
- `io::Cursor::get_ref`
- `io::Cursor::position`
- `io::empty`
- `io::repeat`
- `io::sink`

r? `````@dtolnay`````

use single char patterns for split() (clippy::single_char_pattern)

…lcnr

Small cleanup in `TypeFoldable` derive macro

r? ```@lcnr```

…k-Simulacrum

Honor the rustfmt setting in config.toml

Prior to this, setting the rustfmt configuration was ignored:

```
% mkdir example

% cd example

% ../configure --set build.rustfmt=/usr/bin/true

% ../x.py fmt
./x.py fmt is not supported on this channel
failed to run: /Users/shep/Projects/rust/example/build/bootstrap/debug/bootstrap fmt
Build completed unsuccessfully in 0:00:01
```

And after:

```
% ../x.py fmt
Build completed successfully in 0:00:11
```

r? `@Mark-Simulacrum`

Less verbose debug logging from inlining integrator

The inlining integrator produces relatively verbose and uninteresting
logs.  Move them from a debug log level to a trace level, so that they
can be easily isolated from others.

Convert a bunch of intra-doc links

An intra-doc link bonanza!

This was accomplished using a bunch of trial-and-error with sed.

…ulacrum

rustc_resolve: Use `#![feature(format_args_capture)]`

This is the best new sugar for quite some time.

(I only changed places that already used named arguments.)

typo and formatting

fixed a typo and modified some line formatting justification while I'm here :)

…ow, r=varkor

Don't fire `CONST_ITEM_MUTATION` lint when borrowing a deref

Fixes rust-lang#78819

This extends the check for dereferences added in PR rust-lang#77324
to cover mutable borrows, as well as direct writes. If we're operating
on a dereference of a `const` item, we shouldn't be firing the lint.