Rollup merge of #127677 - onur-ozkan:use-correct-modes, r=Kobzol

using correct tool mode for `run-make-support` crate

We don't need to ensure std (and rustc) for testing run-make-support's unit tests. Using stage 0 compiler is already enough and speeds up `x test run-make-support` invocations on a clean build.

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

@@ -682,6 +682,8 @@ impl Step for CompiletestTest {
         let mut cargo = tool::prepare_tool_cargo(
             builder,
             compiler,
+            // compiletest uses libtest internals; make it use the in-tree std to make sure it never breaks
+            // when std sources change.
             Mode::ToolStd,
             host,
             "test",
@@ -1321,13 +1323,12 @@ impl Step for CrateRunMakeSupport {
     /// Runs `cargo test` for run-make-support.
     fn run(self, builder: &Builder<'_>) {
         let host = self.host;
-        let compiler = builder.compiler(builder.top_stage, host);
+        let compiler = builder.compiler(0, host);
 
-        builder.ensure(compile::Std::new(compiler, host));
         let mut cargo = tool::prepare_tool_cargo(
             builder,
             compiler,
-            Mode::ToolStd,
+            Mode::ToolBootstrap,
             host,
             "test",
             "src/tools/run-make-support",