Rollup merge of rust-lang#129943 - onur-ozkan:test-float-parse-compil…

…er, r=Kobzol

use the bootstrapped compiler for `test-float-parse` test

Fixes rust-lang#122709 (comment).

Blocker for rust-lang#122709

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

@@ -3526,11 +3526,13 @@ impl Step for TestFloatParse {
 
     fn run(self, builder: &Builder<'_>) {
         let bootstrap_host = builder.config.build;
-        let compiler = builder.compiler(0, bootstrap_host);
+        let compiler = builder.compiler(builder.top_stage, bootstrap_host);
         let path = self.path.to_str().unwrap();
         let crate_name = self.path.components().last().unwrap().as_os_str().to_str().unwrap();
 
-        builder.ensure(compile::Std::new(compiler, self.host));
+        if !builder.download_rustc() {
+            builder.ensure(compile::Std::new(compiler, self.host));
+        }
 
         // Run any unit tests in the crate
         let cargo_test = tool::prepare_tool_cargo(