Auto merge of #95254 - jyn514:fix-windows-builds, r=Mark-Simulacrum

Fix `cargo run` on Windows

Fixes the following error:
```
error: failed to run custom build command for `bootstrap v0.0.0 (C:\Users\Walther\git\rust\src\bootstrap)`

Caused by:
  process didn't exit successfully: `C:\Users\Walther\git\rust\target\debug\build\bootstrap-7757a4777dec0f86\build-script-build` (exit code: 101)
  --- stdout
  cargo:rerun-if-changed=build.rs
  cargo:rerun-if-env-changed=RUSTC
  cargo:rustc-env=BUILD_TRIPLE=x86_64-pc-windows-msvc
  cargo:rerun-if-env-changed=PATH

  --- stderr
  thread 'main' panicked at 'assertion failed: rustc.is_absolute()', src\bootstrap\build.rs:22:5
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
warning: build failed, waiting for other jobs to finish...
error: build failed
```

The problem was that the `dir.join` check only works with `rustc.exe`, not `rustc`.

Thanks `@Walther` for the help testing the fix!

Helps with https://github.com/rust-lang/rust/issues/94829.

0 files changed, 0 insertions, 0 deletions