Cargo will always output something on success:
```
$ cargo check --message-format=json
{"reason":"compiler-artifact", ... snipped ... }
{"reason":"build-finished","success":true}
```
However, rustc does not output anything on success:
```
$ rustc --error-format=json main.rs
$ echo $?
0
```
Restore the behaviour prior to #10517, where an exit code of 0 is
considered good even if nothing is written to stdout.
This enables custom overrideCommand values that use rustc rather than
cargo.
The thread name is shown in debugger as well as panic messages and this
patch makes it easier to follow a thread instead of looking through
full backtrace, by naming all spawned threads according to their
functioning.
Cargo commands are affected by the `.cargo/config` files above
their working directory. If cargo is invoked from above the directory
holding `Cargo.toml`, it may not pick up important settings like
registry replacements, causing it to behave differently or even fail.
Most cargo invocations are currently setting their working directories
to the directory containing `Cargo.toml`, but a couple of paths remain
in which cargo is invoked from the default workspace root instead.
This change fixes that, resolving some cargo check failures that I
experienced in a multi-root workspace in which packages used different
registries.
Without this users have no clue why flycheck fails to run.
This is what is printed to the output channel:
```
[ERROR rust_analyzer::main_loop] cargo check failed: Cargo watcher failed,the command produced no valid metadata (exit code: ExitStatus(ExitStatus(25856)))
```
I stumbled with this figuring out that rust-analyzer adds `--all-features` which is not intended
for some crates in the workspace (e.g. they have mutually-exclusive features.
Having the command rust-analyzer ran should help a lot
