Improve context of bootstrap errors in CI

src/bootstrap/src/core/builder/cargo.rs

@@ -101,6 +101,7 @@ pub struct Cargo {
 impl Cargo {
  /// Calls [`Builder::cargo`] and [`Cargo::configure_linker`] to prepare an invocation of `cargo`
  /// to be run.
+ #[track_caller]
  pub fn new(
  builder: &Builder<'_>,
  compiler: Compiler,
@@ -139,6 +140,7 @@ impl Cargo {
 
  /// Same as [`Cargo::new`] except this one doesn't configure the linker with
  /// [`Cargo::configure_linker`].
+ #[track_caller]
  pub fn new_for_mir_opt_tests(
  builder: &Builder<'_>,
  compiler: Compiler,
@@ -396,6 +398,7 @@ impl From<Cargo> for BootstrapCommand {
 
 impl Builder<'_> {
  /// Like [`Builder::cargo`], but only passes flags that are valid for all commands.
+ #[track_caller]
  pub fn bare_cargo(
  &self,
  compiler: Compiler,
@@ -480,6 +483,7 @@ impl Builder<'_> {
  /// scoped by `mode`'s output directory, it will pass the `--target` flag for the specified
  /// `target`, and will be executing the Cargo command `cmd`. `cmd` can be `miri-cmd` for
  /// commands to be run with Miri.
+ #[track_caller]
  fn cargo(
  &self,
  compiler: Compiler,

src/build_helper/src/util.rs

@@ -3,6 +3,8 @@ use std::io::{BufRead, BufReader};
 use std::path::Path;
 use std::process::Command;
 
+use crate::ci::CiEnv;
+
 /// Invokes `build_helper::util::detail_exit` with `cfg!(test)`
 ///
 /// This is a macro instead of a function so that it uses `cfg(test)` in the *calling* crate, not in build helper.
@@ -20,6 +22,15 @@ pub fn detail_exit(code: i32, is_test: bool) -> ! {
  if is_test {
  panic!("status code: {code}");
  } else {
+ // If we're in CI, print the current bootstrap invocation command, to make it easier to
+ // figure out what exactly has failed.
+ if CiEnv::is_ci() {
+ // Skip the first argument, as it will be some absolute path to the bootstrap binary.
+ let bootstrap_args =
+ std::env::args().skip(1).map(|a| a.to_string()).collect::<Vec<_>>().join(" ");
+ eprintln!("Bootstrap failed while executing `{bootstrap_args}`");
+ }
+
  // otherwise, exit with provided status code
  std::process::exit(code);
  }