Auto merge of rust-lang#138224 - onur-ozkan:fix-multiple-candidates, r=jieyouxu

skip `compile::Std` and `compile::Rustc` on `forced_compiler`

Fixes rust-lang#138220

Set `download-rustc = true/false` and run `x test tests/ui/meta/no_std-extern-libc.rs --force-rerun` to debug it.

Author: bors

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

@@ -121,10 +121,18 @@ impl Step for ToolBuild {
 
         match self.mode {
             Mode::ToolRustc => {
-                builder.ensure(compile::Std::new(self.compiler, self.compiler.host));
-                builder.ensure(compile::Rustc::new(self.compiler, target));
+                // If compiler was forced, its artifacts should be prepared earlier.
+                if !self.compiler.is_forced_compiler() {
+                    builder.ensure(compile::Std::new(self.compiler, self.compiler.host));
+                    builder.ensure(compile::Rustc::new(self.compiler, target));
+                }
+            }
+            Mode::ToolStd => {
+                // If compiler was forced, its artifacts should be prepared earlier.
+                if !self.compiler.is_forced_compiler() {
+                    builder.ensure(compile::Std::new(self.compiler, target))
+                }
             }
-            Mode::ToolStd => builder.ensure(compile::Std::new(self.compiler, target)),
             Mode::ToolBootstrap => {} // uses downloaded stage0 compiler libs
             _ => panic!("unexpected Mode for tool build"),
         }