handle cargo submodule in a lazy-load way

Signed-off-by: onur-ozkan <work@onurozkan.dev>

src/bootstrap/src/core/build_steps/test.rs

@@ -3035,6 +3035,9 @@ impl Step for Bootstrap {
         let compiler = builder.compiler(0, host);
         let _guard = builder.msg(Kind::Test, 0, "bootstrap", host, host);
 
+        // Some tests require cargo submodule to be present.
+        builder.build.update_submodule(Path::new("src/tools/cargo"));
+
         let mut check_bootstrap = Command::new(builder.python());
         check_bootstrap
             .args(["-m", "unittest", "bootstrap_test.py"])

src/bootstrap/src/core/build_steps/tool.rs

@@ -586,6 +586,8 @@ impl Step for Cargo {
     }
 
     fn run(self, builder: &Builder<'_>) -> PathBuf {
+        builder.build.update_submodule(Path::new("src/tools/cargo"));
+
         builder.ensure(ToolBuild {
             compiler: self.compiler,
             target: self.target,

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

@@ -1,5 +1,5 @@
 use crate::core::builder::{Builder, RunConfig, ShouldRun, Step};
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use std::process::Command;
 
 #[derive(Debug, Clone, Hash, PartialEq, Eq)]
@@ -34,6 +34,9 @@ impl Step for Vendor {
             cmd.arg("--versioned-dirs");
         }
 
+        // cargo submodule must be present for `x vendor` to work.
+        builder.build.update_submodule(Path::new("src/tools/cargo"));
+
         // Sync these paths by default.
         for p in [
             "src/tools/cargo/Cargo.toml",