This commit is a result of the discussion on rust-lang#128475 and incorporates
parts of rust-lang#109807 as well. This is all done as a new page of
documentation for the `wasm32-unknown-unknown` target which previously
did not exist. This new page goes into details about the preexisting
target and additionally documents the expectations for WebAssembly
features and code generation.

The tl;dr is that LLVM will enable features over time after most engines
have had support for awhile. Compiling without features requires
`-Ctarget-cpu=mvp` to rustc plus `-Zbuild-std` to Cargo.

Closes rust-lang#109807
Closes rust-lang#128475

Co-authored-by: Mark Rousskov <mark.simulacrum@gmail.com>

Co-authored-by: Jubilee <46493976+workingjubilee@users.noreply.github.com>

also make it fail if there's a compression issue

zlib is seemingly always enabled, so we can test it unconditionally

it now checks zlib and zstd, via rustc and rust-lld

move it where it's used, and name it like the other scripts

but warn about it

Co-authored-by: Josh Stone <cuviper@gmail.com>

…avidtwco

Implement `-Z embed-source` (DWARFv5 source code embedding extension)

Implement rust-lang/compiler-team#764 MCP which adds an unstable flag that exposes LLVM's [DWARFv5 source code embedding](https://dwarfstd.org/issues/180201.1.html) support.

…jieyouxu

Document WebAssembly target feature expectations

This commit is a result of the discussion on rust-lang#128475 and incorporates parts of rust-lang#109807 as well. This is all done as a new page of documentation for the `wasm32-unknown-unknown` target which previously did not exist. This new page goes into details about the preexisting target and additionally documents the expectations for WebAssembly features and code generation.

The tl;dr is that LLVM will enable features over time after most engines have had support for awhile. Compiling without features requires `-Ctarget-cpu=mvp` to rustc plus `-Zbuild-std` to Cargo.

Closes rust-lang#109807
Closes rust-lang#119811
Closes rust-lang#128475

More work on `zstd` compression

r? ```@Kobzol``` as we've discussed this.

This is a draft to show the current approach of supporting zstd in compiletest, and making the tests using it unconditional.

Knowing whether llvm/lld was built with `LLVM_ENABLE_ZSTD` is quite hard, so there are two strategies. There are details in the code, and we can discuss this approach. Until we know the config used to build CI artifacts, it seems our options are somewhat limited in any case.

zlib compression seems always enabled, so we only check this in its dedicated test, allowing the test to ignore errors due to zstd not being supported.

The zstd test is made unconditional in what it tests, by relying on `needs-llvm-zstd` to be ignored when `llvm.libzstd` isn't enabled in `config.toml`.

try-job: x86_64-gnu

…r=cuviper

Add a missing compatibility note in the 1.80.0 release notes

rust-lang#99969 missed being included in the release notes. As discussed [on Zulip](https://rust-lang.zulipchat.com/#narrow/stream/241545-t-release/topic/.2399969.20missed.20the.20release.20notes/near/463002451).

(the discussion about the _a posteriori_ breakage the ecosystem is experiencing is another topic)

Thanks

r? ```@rust-lang/release```

…piler-errors

Use a LocalDefId in ResolvedArg.

…ler-errors

Fix handling of macro arguments within the `dropping_copy_types` lint

This PR fixes the handling of spans with different context (aka macro arguments) than the primary expression within the different `{drop,forget}ing_copy_types` and `{drop,forget}ing_references` lints.

<details>
<summary>Before</summary>

```
warning: calls to `std::mem::drop` with a value that implements `Copy` does nothing
 --> drop_writeln.rs:5:5
  |
5 |     drop(writeln!(&mut msg, "test"));
  |     ^^^^^--------------------------^
  |          |
  |          argument has type `Result<(), std::fmt::Error>`
  |
  = note: `#[warn(dropping_copy_types)]` on by default
help: use `let _ = ...` to ignore the expression or result
 --> /home/[..]/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/core/src/macros/mod.rs:688:9
  |
68|         let _ =
  |         ~~~~~~~
```

</details>

<details>
<summary>With this PR</summary>

```
warning: calls to `std::mem::drop` with a value that implements `Copy` does nothing
 --> drop_writeln.rs:5:5
  |
5 |     drop(writeln!(&mut msg, "test"));
  |     ^^^^^--------------------------^
  |          |
  |          argument has type `Result<(), std::fmt::Error>`
  |
  = note: `#[warn(dropping_copy_types)]` on by default
help: use `let _ = ...` to ignore the expression or result
  |
5 -     drop(writeln!(&mut msg, "test"));
5 +     let _ = writeln!(&mut msg, "test");
  |
```

</details>

```@rustbot``` label +L-dropping_copy_types

Don't trigger refinement lint if predicates reference errors

Fixes rust-lang#129404