instrument-coverage was ICEing for me on some code, in particular code
that had devirtualized paths from standard library. Instrument coverage
probably has no bussiness dictating which paths are valid and which
aren't so just feed it everything and whatever and let tooling deal with
other stuff.
For example, with this commit we can generate coverage hitpoints for
these interesting paths:
* `/rustc/.../library/core/lib.rs` – non-devirtualized path for libcore
* `/home/.../src/library/core/lib.rs` – devirtualized version of above
* `<inline asm>`, `<anon>` and many similar synthetic paths
Even if those paths somehow get to the instrumentation pass, I'd much
rather get hits for these weird paths and hope some of them work (as
would be the case for devirtualized path to libcore), rather than have
compilation fail entirely.
Prevent miscompilation in trivial loop {}
Ideally, we would want to handle a broader set of cases to fully fix the
underlying bug here. That is currently relatively expensive at compile and
runtime, so we don't do that for now.
Performance results indicate this is not a major regression, if at all, so it should be safe to land.
cc #28728
Add settings to rustdoc to use the system theme
This PR adds new settings to `rustdoc` to use the operating system color scheme.

`rustdoc` actually had [basic support for this](b1af43bc63/src/librustdoc/html/static/storage.js (L121)), but the setting wasn't visible and couldn't be set back once the theme was explicitly set by the user. It also didn't update if the operating system theme preference changed while viewing a page.
I'm using [this method](https://developer.mozilla.org/en-US/docs/Web/CSS/Media_Queries/Testing_media_queries#Receiving_query_notifications) to query and listen to changes to the `(prefers-color-scheme: dark)` media query. I kept the old method (based on `getComputedStyle`) as a fallback in case the user-agent doesn't support `window.matchMedia` (so like... [pretty much nobody](https://caniuse.com/?search=matchMedia)).
Since there's now more than one official ""dark"" theme in `rustdoc` (and also to support custom/third-party themes), the preferred dark and light themes can be configured in the settings page (the defaults are just "dark" and "light").
This is also my very first "proper" PR to Rust! Please let me know if I did anything wrong :).
Sync from rust
Fix rustc breakage by running:
```rust
git subtree push -P src/tools/clippy git@github.com:josephlr/rust-clippy sync-from-rust
```
and then adding a commit that runs `cargo dev fmt`
---
changelog: none
Vxworks / Unix deduplication
`sys/vxworks` was almost entirely an (outdated) copy of `sys/unix`. I went through every file to check the differences and tried to figure out if they were simply outdated or intentional differences between `unix` and `vxworks`. Most of them did not have any `vxworks`-specific changes, so are deleted. I've added some minor `cfg(target_os = "vxworks")`-specific things to `sys/unix` to allow for deduplication.
Before this change, the vxworks target didn't compile because its outdated process implementation did not match the expected interface anymore. This also fixes that: `std` compiles again for `x86_64-wrs-vxworks`.
It's probably good to merge `sys/vxworks` entirely into `sys/unix`, but it might be better to to that in a follow-up PR.
`@rustbot` modify labels: +T-libs +C-cleanup
This resolves issues where the cross-build of LLVM fails because it tries to
link to the host's system libraries instead of the target's system libraries.
Remove arena's dependency on `rustc_data_structures`
`rustc_arena` currently has a dependency on `rustc_data_structures` because of a trivial "don't inline me" function. This PR copies that function and removes the dependency.