Rollup merge of rust-lang#128822 - onur-ozkan:add-build-config-in-tarballs, r=Kobzol

add `builder-config` into tarball sources

This will be useful for certain scenarios where developers want to know how the tarball sources were generated. We also want this to check for CI rustc incompatible options on bootstrap.

Blocker for rust-lang#122709

r? Kobzol

Author: GuillaumeGomez

src/bootstrap/src/core/config/config.rs

@@ -1325,7 +1325,11 @@ impl Config {
         // Give a hard error if `--config` or `RUST_BOOTSTRAP_CONFIG` are set to a missing path,
         // but not if `config.toml` hasn't been created.
         let mut toml = if !using_default_path || toml_path.exists() {
-            config.config = Some(toml_path.clone());
+            config.config = Some(if cfg!(not(feature = "bootstrap-self-test")) {
+                toml_path.canonicalize().unwrap()
+            } else {
+                toml_path.clone()
+            });
             get_toml(&toml_path)
         } else {
             config.config = None;

src/bootstrap/src/utils/tarball.rs

@@ -317,6 +317,12 @@ impl<'a> Tarball<'a> {
             channel::write_commit_hash_file(&self.overlay_dir, &info.sha);
             channel::write_commit_info_file(&self.overlay_dir, info);
         }
+
+        // Add config file if present.
+        if let Some(config) = &self.builder.config.config {
+            self.add_renamed_file(config, &self.overlay_dir, "builder-config");
+        }
+
         for file in self.overlay.legal_and_readme() {
             self.builder.install(&self.builder.src.join(file), &self.overlay_dir, 0o644);
         }