Rollup merge of #157014 - bjorn3:source_tarball_offline, r=jieyouxu

Allow building the source tarballs while offline

Previously locally vendored dependencies wouldn't be reused when building the source tarball, instead everything would be downloaded from the internet again (if not in the cargo cache).

Fixes #156982

Author: matthiaskrgr

src/bootstrap/src/core/build_steps/vendor.rs

@@ -114,6 +114,13 @@ impl Step for Vendor {
                 cmd.arg("--sync").arg(sync_arg);
             }
 
+            // Reuse vendored dependencies when building source tarball for offline support.
+            if builder.config.vendor {
+                cmd.arg("--respect-source-config")
+                    .arg("--config")
+                    .arg(builder.src.join(".cargo").join("config.toml"));
+            }
+
             // Will read the libstd Cargo.toml
             // which uses the unstable `public-dependency` feature.
             cmd.env("RUSTC_BOOTSTRAP", "1");
@@ -135,6 +142,13 @@ impl Step for Vendor {
             cmd.arg("--versioned-dirs");
         }
 
+        // Reuse vendored dependencies when building source tarball for offline support.
+        if builder.config.vendor {
+            cmd.arg("--respect-source-config")
+                .arg("--config")
+                .arg(builder.src.join("library").join(".cargo").join("config.toml"));
+        }
+
         // Will read the libstd Cargo.toml
         // which uses the unstable `public-dependency` feature.
         cmd.env("RUSTC_BOOTSTRAP", "1");