Auto merge of rust-lang#95253 - jyn514:cargo-run, r=Mark-Simulacrum

Make it possible to run `cargo test` for bootstrap

Note that this only runs bootstrap's self-tests, not compiler or library tests.

Helps with rust-lang#94829.

src/bootstrap/builder/tests.rs

@@ -8,12 +8,9 @@ fn configure(cmd: &str, host: &[&str], target: &[&str]) -> Config {
  config.save_toolstates = None;
  config.dry_run = true;
  config.ninja_in_file = false;
- config.out = PathBuf::from(env::var_os("BOOTSTRAP_OUTPUT_DIRECTORY").unwrap());
- config.initial_rustc = PathBuf::from(env::var_os("RUSTC").unwrap());
- config.initial_cargo = PathBuf::from(env::var_os("BOOTSTRAP_INITIAL_CARGO").unwrap());
  // try to avoid spurious failures in dist where we create/delete each others file
- let dir = config
-  .out
+ // HACK: rather than pull in `tempdir`, use the one that cargo has conveniently created for us
+ let dir = Path::new(env!("OUT_DIR"))
  .join("tmp-rustbuild-tests")
  .join(&thread::current().name().unwrap_or("unknown").replace(":", "-"));
  t!(fs::create_dir_all(&dir));

src/bootstrap/lib.rs

@@ -454,7 +454,7 @@ impl Build {
  .map(PathBuf::from)
  .unwrap_or_else(|_| src.join("target"));
  let bootstrap_out = workspace_target_dir.join("debug");
- if !bootstrap_out.join("rustc").exists() {
+ if !bootstrap_out.join("rustc").exists() && !cfg!(test) {
  // this restriction can be lifted whenever https://github.com/rust-lang/rfcs/pull/3028 is implemented
  panic!("run `cargo build --bins` before `cargo run`")
  }

src/bootstrap/test.rs

@@ -2368,10 +2368,6 @@ impl Step for Bootstrap {
  .current_dir(builder.src.join("src/bootstrap"))
  .env("RUSTFLAGS", "-Cdebuginfo=2")
  .env("CARGO_TARGET_DIR", builder.out.join("bootstrap"))
- // HACK: bootstrap's tests want to know the output directory, but there's no way to set
- // it except through config.toml. Set it through an env variable instead.
- .env("BOOTSTRAP_OUTPUT_DIRECTORY", &builder.config.out)
- .env("BOOTSTRAP_INITIAL_CARGO", &builder.config.initial_cargo)
  .env("RUSTC_BOOTSTRAP", "1")
  .env("RUSTC", &builder.initial_rustc);
  if let Some(flags) = option_env!("RUSTFLAGS") {