… documentation clearly states that negative indexes will cause error.

Just making the code in the example to return Result::Ok, instead of Result::Error.

Also replace a few `hir_node()` calls with `hir_node_by_def_id()`

Instead of executing the test builder directly, the test builder wrapper
will be called with test builder as the first argument and subsequent
arguments. This is similar to cargo's RUSTC_WRAPPER argument.

The `--test-builder-wrapper` argument can be passed multiple times to
allow "nesting" of wrappers.

Also reword "test-builder-wrapper" argument help.

This avoids unnecessary allocation with a temporary Vec.

…illaumeGomez

rustdoc: add `--test-builder-wrapper` arg to support wrappers such as RUSTC_WRAPPER when building doctests

Currently, `rustdoc` builds test crates with `rustc` directly instead of using [`RUSTC_WRAPPER`](https://doc.rust-lang.org/cargo/reference/config.html#buildrustc-wrapper) (if any is set).

This causes build issues in build systems that use `cargo` but tweak linking flags by setting the `RUSTC_WRAPPER` environment variable.

This change is not meant to be final--it's only a minimal proof of concept.
Please advise on the best way to proceed.

Open questions:
- [x] Does supporting the `rustc` wrappers make sense?
    - yes, `cargo-miri` for example needs a "hack" to workaround the issue
- [X] What environment variable(s) should be read for the rustc wrapper? Should `rustdoc` [use the same names as `cargo`](https://doc.rust-lang.org/cargo/reference/config.html#buildrustc-wrapper)?
    - None, since `rustdoc` takes arguments
- [X] What name should be used for a `rustdoc` CLI option?
    - `--test-builder-wrapper`
- [X] Should a separate workspace wrapper (like `RUSTC_WORKSPACE_WRAPPER`) be supported?
    - `--test-builder-wrapper` can be passed multiple times to get multiple wrappers passed
- [X] How/where should this be documented? It's not obvious to all users that `cargo doc` actually causes `rustdoc` to compile tests with rust
    - Added doc to `src/doc/rustdoc/src/command-line-arguments.md` per `@GuillaumeGomez`

…anup, r=Nadrieril

Cleanup `MirBorrowckCtxt::prefixes`

Some of the uses of this method aren't necessary anymore and `PrefixSet::Supporting` is not used anywhere.

With `PrefixSet::Supporting` removed, this could technically be moved to an extension trait on `PlaceRef`. However, it would have to be moved back to `MirBorrowckCtxt` when the `Derefer` MIR pass is moved before borrowck so I didn't.

…gs, r=Mark-Simulacrum

Greatly reduce GCC build logs

Fixes rust-lang/rust-log-analyzer#80.

Based on [makefile documentation](https://www.gnu.org/software/make/manual/html_node/Options-Summary.html#index-_002d_002dquiet-1) and [configure documentation](https://www.gnu.org/software/autoconf/manual/autoconf-2.68/html_node/configure-Invocation.html).

cc `@RalfJung` `@antoyo`

…tation-fix, r=Nilstrieb

Cursor.rs documentation fix

Reason:

I've been learning Rust std library and got confused. Seek trait documentation clearly states that negative indexes will cause an error. And the code in the Cursor example uses negative index. I found myself trying to understand what am I missing until I've actually executed the code and got error. I decided to submit small fix to the documentation.

hir: Remove `opt_local_def_id_to_hir_id` and `opt_hir_node_by_def_id`

Also replace a few `hir_node()` calls with `hir_node_by_def_id()`.

Follow up to rust-lang#120943.

less symbol interner locks

This reduces instructions under 1% (in rustdoc run), but essentially free.