Deleted unused labels from compiler and fixed or allowed
unused labels in tests. This patch removes some gratuitous
unused labels and turns off the warning for unused labels
that are a necessary part of tests.  This will permit
setting the `unused_labels` lint to `warn`.

Closes rust-lang#66324.

The build process of the unikernel HermitCore is redesigned and
doesn't longer depend on libhermit.

…nneeded Index impl, remove body fn

rustc_codegen_ssa: Fix BodyAndCache reborrow to Body and change instances of body() call to derefence
rustc_mir: Fix BodyAndCache reborrow to Body and change intances of body() call to derefence

`legacy_disrectory_ownership` vs `legacy_directory_ownership`

Change unused_labels from allow to warn

Fixes rust-lang#66324, making the unused_labels lint warn instead of allow by default. I'm told @rust-lang/lang will need to review this, and perhaps will want to do a crater run.

remove dependency from libhermit

The build process of the unikernel HermitCore is redesigned and doesn't longer depend on libhermit.

Format libcore with rustfmt (including tests and benches)

Important: two small non-rustfmt changes that will need close review:

- I added `#[rustfmt::skip]` to two manually arranged tables in src/libcore/benches/ascii.rs; see first commit in the PR.
- I added `// ignore-tidy-filelength` to src/libcore/ptr/mod.rs because rustfmt puts it over tidy's 3000 line limit; see second commit in the PR. I filed rust-lang#66891 to follow up on breaking up that file. For now though having it be formatted is more important than having it below the line limit.

---

As with my previous formatting PRs, I am avoiding causing merge conflicts in other PRs by only touches those files that are not involved in any currently open PR. Files that appear in new PRs between when this PR is opened and when it makes it to the top of the bors queue will be reverted from this PR.

The list of files involved in open PRs is determined by querying GitHub's GraphQL API [with this script](https://gist.github.com/dtolnay/aa9c34993dc051a4f344d1b10e4487e8).

With the list of files from the script in outstanding_files, the relevant commands were:

```
$ find src/libcore -name '*.rs' \
    | xargs rustfmt --edition=2018 --unstable-features --skip-children
$ rg libcore outstanding_files | xargs git checkout --
```

To confirm no funny business:

```
$ git checkout $THIS_COMMIT^
$ git show --pretty= --name-only $THIS_COMMIT \
    | xargs rustfmt --edition=2018 --unstable-features --skip-children
$ git diff $THIS_COMMIT  # there should be no difference
```

r? @Dylan-DPC

Standard library support for riscv64gc-unknown-linux-gnu

Add std support for RISC-V 64-bit GNU/Linux and update libc for RISC-V support.

r? @alexcrichton

Cleanup BodyCache

After this PR:

- `BodyCache` is renamed to `BodyAndCache`
- `ReadOnlyBodyCache` is renamed to `ReadOnlyBodyAndCache`
- `ReadOnlyBodyAndCache::body` fn is removed and all calls to it are replaced by a deref (possible due to fix of its `Deref` imp in rust-lang#65947)

cc @eddyb @oli-obk

…chenkov

Make `ForeignItem` an alias of `Item`.

Working towards the merging of items in AST and syntactically.

r? @petrochenkov

Fixes typo

`legacy_disrectory_ownership` vs `legacy_directory_ownership`