Fix docs for OsStr

At present, there are two small issues with the [docs](https://doc.rust-lang.org/std/ffi/struct.OsStr.html) for std::ffi::OsStr:
- The docs say "OsStr is to OsString as String is to &str: the former in each pair are borrowed references; the latter are owned strings.". The latter pair is mixed up: String is the owned variant whereas &str is the borrowed reference.
- The doc links to String and &str are broken and render as [String] and [&str].

This PR fixes these issues.

Make libtest build on CloudABI.

Just like on UNIX systems, we need to use sysconf() to obtain the number
of CPUs. Extend the existing cfg()'s to match CloudABI as well.

Add tests to fixed issues.

Closes #36792. Closes #38091. Closes #39687. Closes #42148. Closes #42956.

Glued tokens can themselves be joint.

When gluing two tokens, the second of which is joint, the result should also be
joint.
This fixes an issue with joining three `Dot` tokens to make a `DotDotDot` - the
intermediate `DotDot` would not be joint and therefore we would not attempt to
glue the last `Dot` token, yielding `.. .` instead of `...`.

r? @jseyfried

Fix typo.

Add -Ztime-passes line for dep-graph loading.

We measure how much time the background thread spends on loading the dep-graph but not how long the main thread is blocked while the background thread is still working. Let's change that!

Use the new fs_read_write functions in rustc internals

Uses `fs::read` and `fs::write` (added by #45837) where appropriate, to simplify code and dog-food these new APIs.  This also improves performance, when combined with #47324.

Pre-allocate in fs::read and fs::read_string

This is a simpler alternative to #46340 and #45928, as requested by the libs team.

fix typo rwlock.rs

Hi. Fixed typo: contained -> content

Fix panic strings.

 - Fix panic string in `check_ast_crate`.
 - Update panic string for Duration subtraction on overflow/underflow.

Not sure if the changes to `Duration` are helpful/needed. Mostly just a nit.
Otherwise this is just a one character change :)

On another note: I hit the panic in `check_ast_crate` when compiling
[m-labs/smoltcp] with the following:

```
cargo test --doc --no-default-features --features "std socket-raw"`
```

[m-labs/smoltcp]: https://github.com/m-labs/smoltcp

Don't track local_needs_drop separately in qualify_consts.

None

Use copy/clone closures to simplify calendar test

Split out from #47304

r? @EddyB

Treat #[path] files as mod.rs files

Fixes https://github.com/rust-lang/rust/issues/46936, cc @briansmith, @SergioBenitez, @nikomatsakis.

This (insta-stable) change treats files included via `#[path = "bla.rs"] mod foo;` as though they were `mod.rs` files. Namely, it allows them to include `mod` statements and looks for the child modules in sibling directories, rather than in relative `modname/childmodule.rs` files as happens for non-`mod.rs` files.

This change makes the `non_modrs_mods` feature backwards compatible with the existing usage in https://github.com/briansmith/ring, several versions of which are currently broken in beta. If we decide to merge, this change should be backported to beta.

cc https://github.com/rust-lang/rust/issues/37872

r? @jseyfried

Skip linker-output-non-utf8 test on Apple

This test fails on APFS filesystems with the following error:

```shell
mkdir: /Users/ryan/Code/rust/build/x86_64-apple-darwin/test/run-make/linker-output-non-utf8.stage2-x86_64-apple-darwin/zzz�: Illegal byte sequence
```

The mkdir does succeed on an HFS+ volume mounted on the same system:
```shell
$ mkdir zzz$$'\xff'
$ ls
zzz47432\xff
```

This is due to APFS now requiring that all paths are valid UTF-8. As APFS will be the default filesystem for all new Darwin-based systems the most straightforward fix is to skip this test on Darwin as well as Windows.

Update jobserver to 0.1.9

Fix for `ENOSYS` when calling `pipe2`, alexcrichton/jobserver-rs#5.

r? @alexcrichton

Update musl to 1.1.18

According to http://www.musl-libc.org/download.html:

This release corrects regressions in glob() and armv4t build failure
introduced in the previous release, and includes an important bug fix
for posix_spawnp in the presence of a large PATH environment variable.

Add i586-unknown-linux-musl target

Show only stderr diff when a ui test fails

Addresses #46826.

This PR will print the normalized output if expected text is empty otherwise it will just print the diff.

Should we also show a few (actual == expected) lines above & below when displaying the diff? What about indicating line numbers as well so one can quickly check mismatch lines in .stderr file?

Fix nested imports not included in the save_analysis output

This PR fixes #46823.

The bug was caused by the old access level checking code, which checked against the root UseTree even for nested trees. The problem with that is, for nested trees the root is lowered as an empty `ListStem`, which is not reachable by definition. The new code computes the access level with each tree's own ID, and with the root tree's visibility.

I tested this manually and it works, but I'm not really satisfied with that. I looked at the existing tests though, and no one checked for the save_analysis output as far as I can see. How should I proceed with that? I think having a test about this would be really nice.

rustfmt libarena/lib.rs

Note: it's my very first pull request. I'm trying to do something very simple to see how it works here, even if it's a tiny change or maybe it's not correct (sorry if it is the case).

r? @nrc

Implement AsRef<Path> for Component

Fixes #41866

macros: improve 1.0/2.0 interaction

This PR supports using unhygienic macros from hygienic macros without breaking the latter's hygiene.
```rust
// crate A:
#[macro_export]
macro_rules! m1 { () => {
    f(); // unhygienic: this macro needs `f` in its environment
    fn g() {} // (1) unhygienic: `g` is usable outside the macro definition
} }

// crate B:
#![feature(decl_macro)]
extern crate A;
use A::m1;

macro m2() {
    fn f() {} // (2)
    m1!(); // After this PR, `f()` in the expansion resolves to (2), not (3)
    g(); // After this PR, this resolves to `fn g() {}` from the above expansion.
         // Today, it is a resolution error.
}

fn test() {
    fn f() {} // (3)
    m2!(); // Today, `m2!()` can see (3) even though it should be hygienic.
    fn g() {} // Today, this conflicts with `fn g() {}` from the expansion, even though it should be hygienic.
}
```

Once this PR lands, you can make an existing unhygienic macro hygienic by wrapping it in a hygienic macro. There is an [example](https://github.com/rust-lang/rust/pull/46551/commits/b766fa887dc0e4b923a38751fe4d570e35a75710) of this in the tests.

r? @nrc

Add iterator method specialisations to Range*

Add specialised implementations of `max` for `Range`, and `last`, `min` and `max` for `RangeInclusive`, all of which lead to significant advantages in the generated assembly on x86.

Note that adding specialisations of `min` and `last` for `Range` led to no benefit, and adding `sum` for `Range` and `RangeInclusive` led to type inference issues (though this is possibly still worthwhile considering the performance gain).

This addresses some of the concerns in #39975.

Just like on UNIX systems, we need to use sysconf() to obtain the number
of CPUs. Extend the existing cfg()'s to match CloudABI as well.

Closes #36792. Closes #38091. Closes #39687. Closes #42148. Closes #42956.

Replace uses of DepGraph.in_ignore with DepGraph.with_ignore

I currently plan to track tasks in thread local storage. Ignoring things in a closure ensures that the ignore tasks do not overlap the beginning or end of any other task. The TLS API will also use a closure to change a TLS value, so having the ignore task be a closure also helps there.

It also adds `assert_ignored` which is used before a `TyCtxt` is created. Instead of adding a new ignore task this simply ensures that we are in a context where reads are ignored.

r? @michaelwoerister

When gluing two tokens, the second of which is joint, the result should also be
joint.
This fixes an issue with joining three `Dot` tokens to make a `DotDotDot` - the
intermediate `DotDot` would not be joint and therefore we would not attempt to
glue the last `Dot` token, yielding `.. .` instead of `...`.

[incremental] Specialize encoding and decoding of Fingerprints

This saves the storage space used by about 32 bits per `Fingerprint`.
On average, this reduces the size of the `/target/{mode}/incremental`
folder by roughly 5% [Full details here](https://gist.github.com/wesleywiser/264076314794fbd6a4c110d7c1adc43e).

Fixes #45875

r? @michaelwoerister

 - Fix panic string in `check_ast_crate`.

Fix built-in indexing not being used where index type wasn't "obviously" usize

Fixes #33903
Fixes #46095

This PR was made possible thanks to the generous help of @EddyB

Following the example of binary operators, builtin checking for indexing has been moved from the typecheck stage to a writeback stage, after type constraints have been resolved.

Implement `Write` for `Cursor<&mut Vec<T>>`

Fixes #30132

r? @dtolnay (I'm just going through `feature-accepted` issues I swear 😛)