Make Cargo a rustc tool again

src/bootstrap/test.rs

@@ -213,7 +213,7 @@ fn run(self, builder: &Builder<'_>) {
         });
         let mut cargo = tool::prepare_tool_cargo(builder,
                                                  compiler,
-                                                 Mode::ToolStd,
+                                                 Mode::ToolRustc,
                                                  self.host,
                                                  "test",
                                                  "src/tools/cargo",

src/bootstrap/tool.rs

@@ -514,7 +514,7 @@ fn run(self, builder: &Builder<'_>) -> PathBuf {
             compiler: self.compiler,
             target: self.target,
             tool: "cargo",
-            mode: Mode::ToolStd,
+            mode: Mode::ToolRustc,
             path: "src/tools/cargo",
             is_optional_tool: false,
             source_type: SourceType::Submodule,