rustbuild: Add support for crate tests + doctests

This commit adds support to rustbuild to run crate unit tests (those defined by
`#[test]`) as well as documentation tests. All tests are powered by `cargo test`
under the hood.

Each step requires the `libtest` library is built for that corresponding stage.
Ideally the `test` crate would be a dev-dependency, but for now it's just easier
to ensure that we sequence everything in the right order.

Currently no filtering is implemented, so there's not actually a method of
testing *only* libstd or *only* libcore, but rather entire swaths of crates are
tested all at once.

A few points of note here are:

* The `coretest` and `collectionstest` crates are just listed as `[[test]]`
  entires for `cargo test` to naturally pick up. This mean that `cargo test -p
  core` actually runs all the tests for libcore.
* Libraries that aren't tested all mention `test = false` in their `Cargo.toml`
* Crates aren't currently allowed to have dev-dependencies due to
  rust-lang/cargo#860, but we can likely alleviate this restriction once
  workspaces are implemented.

cc #31590

1 files changed, 9 insertions, 1 deletions

diff --git a/src/bootstrap/rustdoc.rs b/src/bootstrap/rustdoc.rs
index 8c618196113..88ac26d32f6 100644
--- a/src/bootstrap/rustdoc.rs
+++ b/src/bootstrap/rustdoc.rs
@@ -12,17 +12,25 @@
 //!
 //! See comments in `src/bootstrap/rustc.rs` for more information.
 
+extern crate bootstrap;
+
 use std::env;
 use std::process::Command;
+use std::path::PathBuf;
 
 fn main() {
     let args = env::args_os().skip(1).collect::<Vec<_>>();
     let rustdoc = env::var_os("RUSTDOC_REAL").unwrap();
+    let libdir = env::var_os("RUSTC_LIBDIR").unwrap();
+
+    let mut dylib_path = bootstrap::dylib_path();
+    dylib_path.insert(0, PathBuf::from(libdir));
 
     let mut cmd = Command::new(rustdoc);
     cmd.args(&args)
        .arg("--cfg").arg(format!("stage{}", env::var("RUSTC_STAGE").unwrap()))
-       .arg("--cfg").arg("dox");
+       .arg("--cfg").arg("dox")
+       .env(bootstrap::dylib_path_var(), env::join_paths(&dylib_path).unwrap());
     std::process::exit(match cmd.status() {
         Ok(s) => s.code().unwrap_or(1),
         Err(e) => panic!("\n\nfailed to run {:?}: {}\n\n", cmd, e),