Rollup of 5 pull requests

Successful merges:

 - #92887 (Bootstrap compiler update)
 - #92908 (Render more readable macro matcher tokens in rustdoc)
 - #93183 (rustdoc: mobile nav fixes)
 - #93192 (Add VS 2022 into error message)
 - #93475 (Add test to ensure that theme is applied correctly when going back in history)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Add test to ensure that theme is applied correctly when going back in history

Fixes #93258.

r? `@jsha`

Add VS 2022 into error message

rustdoc: mobile nav fixes

- Make sure the mobile-topbar doesn't overflow its height if the user sets a bigger font.

- Make sure the sidebar can be scrolled all the way to the bottom by shortening it to accommodate the mobile-topbar.

- Make the item name in the mobile-topbar clickable to go to the top of the page.

- Remove excess padding sidebar in mobile mode.

Demo https://rustdoc.crud.net/jsha/mobile-nav-fixes/std/string/struct.String.html

r? `@GuillaumeGomez`

Render more readable macro matcher tokens in rustdoc

Follow-up to #92334.

This PR lifts some of the token rendering logic from https://github.com/dtolnay/prettyplease into rustdoc so that even the matchers for which a source code snippet is not available (because they are macro-generated, or any other reason) follow some baseline good assumptions about where the tokens in the macro matcher are appropriate to space.

The below screenshots show an example of the difference using one of the gnarliest macros I could find. Some things to notice:

- In the **before**, notice how a couple places break in between `$(....)`↵`*`, which is just about the worst possible place that it could break.

- In the **before**, the lines that wrapped are weirdly indented by 1 space of indentation relative to column 0. In the **after**, we use the typical way of block indenting in Rust syntax which is put the open/close delimiters on their own line and indent their contents by 4 spaces relative to the previous line (so 8 spaces relative to column 0, because the matcher itself is indented by 4 relative to the `macro_rules` header).

- In the **after**, macro_rules metavariables like `$tokens:tt` are kept together, which is how just about everybody writing Rust today writes them.

## Before

![Screenshot from 2022-01-14 13-05-53](https://user-images.githubusercontent.com/1940490/149585105-1f182b78-751f-421f-a234-9dbc04fa3bbd.png)

## After

![Screenshot from 2022-01-14 13-06-04](https://user-images.githubusercontent.com/1940490/149585118-d4b52ea7-3e67-4b6e-a12b-31dfb8172f86.png)

r? `@camelid`

Bootstrap compiler update

r? ``@Mark-Simulacrum``

Rollup of 8 pull requests

Successful merges:

 - #93256 (Make `join!` description more accurate)
 - #93358 (Add note suggesting that predicate may be satisfied, but is not `const`)
 - #93362 (Do not register infer var for GAT projection in RPIT)
 - #93391 (rustdoc: remove tooltip from source link)
 - #93414 (Move unstable is_{arch}_feature_detected! macros to std::arch)
 - #93441 (rustdoc: load the set of in-scope traits for modules with no docstring)
 - #93459 (fs: Don't copy d_name from struct dirent)
 - #93463 (Rename _args -> args in format_args expansion)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

- Make sure the mobile-topbar doesn't overflow its height if the user
  sets a bigger font.

- Make sure the sidebar can be scrolled all the way to the bottom by
  shortening it to accommodate the mobile-topbar.

- Make the item name in the mobile-topbar clickable to go to the top of
  the page.

- Remove excess padding sidebar in mobile mode.

Rename _args -> args in format_args expansion

As observed in https://github.com/rust-lang/rust/pull/91359#discussion_r786058960, prior to that PR this variable was sometimes never used, such as in the case of:

```rust
println!("");

// used to expand to:
::std::io::_print(
    ::core::fmt::Arguments::new_v1(
        &["\n"],
        &match () {
            _args => [],
        },
    ),
);
```

so the leading underscore in `_args` was used to suppress an unused variable lint. However after #91359 the variable is always used when present, as the unused case would instead expand to:

```rust
::std::io::_print(::core::fmt::Arguments::new_v1(&["\n"], &[]));
```

fs: Don't copy d_name from struct dirent

The dirent returned from readdir() is only guaranteed to be valid for
d_reclen bytes on common platforms.  Since we copy the name separately
anyway, we can copy everything except d_name into DirEntry::entry.

Fixes #93384.

rustdoc: load the set of in-scope traits for modules with no docstring

Fixes #93428

This fix is a response to a couple of special cases related to the `module_id`, which is eventually used for trait candidates:

  * The module id is always set to the current crate, when checking `crate::`.

    Normally, the set of in-scope traits would be set in `load_links_in_attrs`, but if there are no doc comments, then that loop will never run.

  * the module id is set to the parent module, when resolving a module that is spelled like this:

        // Notice how we use an outlined doc comment here!
        // [`Test::my_fn`]
        mod something {
        }

    As with the above problem with `crate::`, we need to make sure the module gets its traits in scope resolved, even if it has no doc comments of its own.

Move unstable is_{arch}_feature_detected! macros to std::arch

These macros are unstable, except for `is_x86_feature_detected` which is still exported from the crate root for backwards-compatibility.

This should unblock the stabilization of `is_aarch64_feature_detected`.

r? ```@m-ou-se```

rustdoc: remove tooltip from source link

This made more sense back when it was abbreviated, but now it seems redundant.

Do not register infer var for GAT projection in RPIT

Fixes #93340
Fixes #91603

r? ```@oli-obk```

Add note suggesting that predicate may be satisfied, but is not `const`

Not sure if we should be printing this in addition to, or perhaps _instead_ of the help message:
```
help: the trait `~const Add` is not implemented for `NonConstAdd`
```

Also added `ParamEnv::is_const` and `PolyTraitPredicate::is_const_if_const` and, in a separate commit, used those in other places instead of `== hir::Constness::Const`, etc.

r? ````@fee1-dead````

Make `join!` description more accurate

The dirent returned from readdir() is only guaranteed to be valid for
d_reclen bytes on common platforms.  Since we copy the name separately
anyway, we can copy everything except d_name into DirEntry::entry.

Fixes #93384.

Rollup of 8 pull requests

Successful merges:

 - #88205 (Add Explanation For Error E0772)
 - #92274 (Add `intrinsics::const_deallocate`)
 - #93236 (Make `NonNull::new` `const`)
 - #93299 (Fix dot separator when there is no source link)
 - #93410 (kmc-solid: Implement `net::FileDesc::duplicate`)
 - #93424 (fix nit)
 - #93431 (remove unused `jemallocator` crate)
 - #93453 (Add GUI theme change test)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

Add GUI theme change test

r? `@jsha`

remove unused `jemallocator` crate

When it was noticed that the rustc binary wasn't actually using jemalloc via `#[global_allocator]` and that was removed, the dependency remained.

Tests pass locally with a `jemalloc = true` build, but I'll trigger a try build to ensure I haven't missed an edge-case somewhere.

r? ```@ghost``` until that completes

fix nit

kmc-solid: Implement `net::FileDesc::duplicate`

This PR implements `std::sys::solid::net::FileDesc::duplicate`, which was accidentally left out when this target was added by #86191.

Fix dot separator when there is no source link

Fixes #92973.

We did well adding this test since there was a bug:

![Screenshot from 2022-01-25 17-05-48](https://user-images.githubusercontent.com/3050060/151016535-39b45f52-e1e0-4963-ad19-532e24ec4c9b.png)

r? `@jsha`

Make `NonNull::new` `const`

Tracking issue: #93235

Add `intrinsics::const_deallocate`

Tracking issue: #79597
Related: #91884

This allows deallocation of a memory allocated by `intrinsics::const_allocate`. At the moment, this can be only used to reduce memory usage, but in the future this may be useful to detect memory leaks (If an allocated memory remains after evaluation, raise an error...?).

Add Explanation For Error E0772

I've added an error explanation for the error code E0772.

Assists with #61137

Add tests for three old ICEs

Closes #84044
Closes #91594
Closes #89066

Bump libc and fix remove_dir_all on Fuchsia after CVE fix

With the previous `is_dir` impl, we would attempt to unlink
a directory in the None branch, but Fuchsia supports returning
ENOTEMPTY from unlinkat() without the AT_REMOVEDIR flag because
we don't currently differentiate unlinking files and directories
by default.

On the Fuchsia side I've opened https://fxbug.dev/92273 to discuss
whether this is the correct behavior, but it doesn't seem like
addressing the error code is necessary to make our tests happy.

Depends on https://github.com/rust-lang/libc/pull/2654 since we
apparently haven't needed to reference DT_UNKNOWN before this.

Move tier-2 (without host tools) apple targets to separate builder

One-off (likely fairly unreliable, but give some idea) measurements:

* dist-apple-various (new):  2h10m
* dist-x86_64-apple: 2h55m -> 2h36m (cutting roughly 20 minutes)

The ICE from #84044 no longer occurs.

Rollup of 10 pull requests

Successful merges:

 - #92611 (Add links to the reference and rust by example for asm! docs and lints)
 - #93158 (wasi: implement `sock_accept` and enable networking)
 - #93239 (Add os::unix::net::SocketAddr::from_path)
 - #93261 (Some unwinding related cg_ssa cleanups)
 - #93295 (Avoid double panics when using `TempDir` in tests)
 - #93353 (Unimpl {Add,Sub,Mul,Div,Rem,BitXor,BitOr,BitAnd}<$t> for Saturating<$t>)
 - #93356 (Edit docs introduction for `std::cmp::PartialOrd`)
 - #93375 (fix typo `documenation`)
 - #93399 (rustbuild: Fix compiletest warning when building outside of root.)
 - #93404 (Fix a typo from #92899)

Failed merges:

r? `@ghost`
`@rustbot` modify labels: rollup

With the previous `is_dir` impl, we would attempt to unlink
a directory in the None branch, but Fuchsia supports returning
ENOTEMPTY from unlinkat() without the AT_REMOVEDIR flag because
we don't currently differentiate unlinking files and directories
by default.

On the Fuchsia side I've opened https://fxbug.dev/92273 to discuss
whether this is the correct behavior, but it doesn't seem like
addressing the error code is necessary to make our tests happy.

Updates std's libc crate to include DT_UNKNOWN for Fuchsia.