Only use the flag for rustc and std

Author: Kobzol

src/bootstrap/src/core/build_steps/compile.rs

@@ -290,14 +290,7 @@ impl Step for Std {
         );
 
         let stamp = build_stamp::libstd_stamp(builder, build_compiler, target);
-        run_cargo(
-            builder,
-            cargo,
-            vec![],
-            &stamp,
-            target_deps,
-            false,
-        );
+        run_cargo(builder, cargo, vec![], &stamp, target_deps, false);
 
         builder.ensure(StdLink::from_std(
             self,

src/bootstrap/src/core/builder/cargo.rs

@@ -1074,7 +1074,9 @@ impl Builder<'_> {
         // Enable usage of unstable features
         cargo.env("RUSTC_BOOTSTRAP", "1");
 
-        cargo.arg("-Zno-embed-metadata");
+        if matches!(mode, Mode::Rustc | Mode::Std) {
+            cargo.arg("-Zno-embed-metadata");
+        }
 
         if self.config.dump_bootstrap_shims {
             prepare_behaviour_dump_dir(self.build);