ensure std for cross-targets

Previously, doing `x test compiler/*` would fail the build due to missing std.
This change ensures that it is prepared.

Signed-off-by: onur-ozkan <work@onurozkan.dev>

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

@@ -2563,9 +2563,13 @@ impl Step for Crate {
         let target = self.target;
         let mode = self.mode;
 
-        // See [field@compile::Std::force_recompile].
-        builder.ensure(compile::Std::force_recompile(compiler, target));
-        builder.ensure(RemoteCopyLibs { compiler, target });
+        builder.ensure(compile::Std::force_recompile(compiler, compiler.host));
+
+        if builder.config.build != target {
+            // See [field@compile::Std::force_recompile].
+            builder.ensure(compile::Std::force_recompile(compiler, target));
+            builder.ensure(RemoteCopyLibs { compiler, target });
+        }
 
         // If we're not doing a full bootstrap but we're testing a stage2
         // version of libstd, then what we're actually testing is the libstd