make dist vendoring configurable

config.example.toml

@@ -942,3 +942,6 @@
 # Copy the linker, DLLs, and various libraries from MinGW into the Rust toolchain.
 # Only applies when the host or target is pc-windows-gnu.
 #include-mingw-linker = true
+
+# Whether to vendor dependencies for the dist tarball.
+#vendor = if "is a tarball source" || "is a git repository" { true } else { false }

src/bootstrap/src/core/build_steps/dist.rs

@@ -1011,11 +1011,7 @@ impl Step for PlainSourceTarball {
         write_git_info(builder.rust_info().info(), plain_dst_src);
         write_git_info(builder.cargo_info.info(), &plain_dst_src.join("./src/tools/cargo"));
 
-        // If we're building from git or tarball sources, we need to vendor
-        // a complete distribution.
-        if builder.rust_info().is_managed_git_subrepository()
-            || builder.rust_info().is_from_tarball()
-        {
+        if builder.config.dist_vendor {
             builder.require_and_update_all_submodules();
 
             // Vendor all Cargo dependencies

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

@@ -308,6 +308,7 @@ pub struct Config {
     pub dist_compression_formats: Option<Vec<String>>,
     pub dist_compression_profile: String,
     pub dist_include_mingw_linker: bool,
+    pub dist_vendor: bool,
 
     // libstd features
     pub backtrace: bool, // support for RUST_BACKTRACE
@@ -933,6 +934,7 @@ define_config! {
         compression_formats: Option<Vec<String>> = "compression-formats",
         compression_profile: Option<String> = "compression-profile",
         include_mingw_linker: Option<bool> = "include-mingw-linker",
+        vendor: Option<bool> = "vendor",
     }
 }
 
@@ -2028,13 +2030,19 @@ impl Config {
                 compression_formats,
                 compression_profile,
                 include_mingw_linker,
+                vendor,
             } = dist;
             config.dist_sign_folder = sign_folder.map(PathBuf::from);
             config.dist_upload_addr = upload_addr;
             config.dist_compression_formats = compression_formats;
             set(&mut config.dist_compression_profile, compression_profile);
             set(&mut config.rust_dist_src, src_tarball);
-            set(&mut config.dist_include_mingw_linker, include_mingw_linker)
+            set(&mut config.dist_include_mingw_linker, include_mingw_linker);
+            config.dist_vendor = vendor.unwrap_or_else(|| {
+                // If we're building from git or tarball sources, enable it by default.
+                config.rust_info.is_managed_git_subrepository()
+                    || config.rust_info.is_from_tarball()
+            });
         }
 
         if let Some(r) = rustfmt {

src/bootstrap/src/utils/change_tracker.rs

@@ -260,4 +260,9 @@ pub const CONFIG_CHANGE_HISTORY: &[ChangeInfo] = &[
         severity: ChangeSeverity::Info,
         summary: "'tools' and 'library' profiles switched `download-ci-llvm` option from `if-unchanged` to `true`.",
     },
+    ChangeInfo {
+        change_id: 130110,
+        severity: ChangeSeverity::Info,
+        summary: "New option `dist.vendor` added to control whether bootstrap should vendor dependencies for dist tarball.",
+    },
 ];