`x check bootstrap` doesn't work

[Kobzol]

x check bootstrap (which essentially does cd src/bootstrap && cargo check --all-targets doesn't compile. Probably there are some issues with test/non-test code when all targets are compiled together.

[Shunpoco]

@Kobzol Does this issue still exist?
I tried ./x check bootstrap on the current head of master but it succeeded.

I also tried it on the commit c720f49c46ec3e70bbc2bbb3e0dd1fe7fc0a47f2, the auto merge commit of your PR #143048. I got some errors:

error[E0433]: failed to resolve: you might be missing crate `core`
 --> src/bootstrap/src/bin/../utils/tests/mod.rs:8:12
  |
8 | use crate::core::builder::Builder;
  |            ^^^^
  |            |
  |            you might be missing crate `core`
  |            help: try using `std` instead of `core`: `std`

error[E0433]: failed to resolve: you might be missing crate `core`
 --> src/bootstrap/src/bin/../utils/tests/mod.rs:9:12
  |
9 | use crate::core::config::DryRun;
  |            ^^^^
  |            |
  |            you might be missing crate `core`
  |            help: try using `std` instead of `core`: `std`

error[E0433]: failed to resolve: unresolved import
  --> src/bootstrap/src/bin/../utils/tests/mod.rs:10:12
   |
10 | use crate::utils::helpers::get_host_target;
   |            ^^^^^
   |            |
   |            unresolved import
   |            help: a similar path exists: `clap_complete::generator::utils`

error[E0432]: unresolved imports `crate::Build`, `crate::Config`, `crate::Flags`, `crate::t`
  --> src/bootstrap/src/bin/../utils/tests/mod.rs:11:13
   |
11 | use crate::{Build, Config, Flags, t};
   |             ^^^^^  ^^^^^^  ^^^^^  ^ no `t` in the root
   |             |      |       |
   |             |      |       no `Flags` in the root
   |             |      no `Config` in the root
   |             no `Build` in the root
   |
   = help: consider importing one of these items instead:
           bootstrap::Build
           bootstrap::Subcommand::Build
           cc::Build
   = help: consider importing one of these structs instead:
           bootstrap::Config
           cmake::Config
   = help: consider importing this struct instead:
           bootstrap::Flags

error: unused import: `Path`
 --> src/bootstrap/src/bin/../utils/tests/mod.rs:3:17
  |
3 | use std::path::{Path, PathBuf};
  |                 ^^^^
  |
  = note: `-D unused-imports` implied by `-D warnings`
  = help: to override `-D warnings` add `#[allow(unused_imports)]`

error: unused import: `std::thread`
 --> src/bootstrap/src/bin/../utils/tests/mod.rs:4:5
  |
4 | use std::thread;
  |     ^^^^^^^^^^^

Some errors have detailed explanations: E0432, E0433.
For more information about an error, try `rustc --explain E0432`.
error: could not compile `bootstrap` (bin "rustdoc" test) due to 6 previous errors
warning: build failed, waiting for other jobs to finish...
error: could not compile `bootstrap` (bin "rustc" test) due to 6 previous errors
Build completed unsuccessfully in 0:01:58

So was the issue somehow solved?

[Kobzol]

It was indeed, and we now even check it on CI, so it shouldn't regress again. Thanks for noticing!