Rollup merge of rust-lang#99293 - jo3bingham:issue-98720-fix, r=jyn514

only run --all-targets in stage0 for Std

Repro'd the issue with `python3 x.py check --stage 1 library/std` and tested the fix with the same command.

r? `@jyn514`

I tried to implement [this solution](rust-lang#98720 (comment)), but didn't have any luck. I don't think I fully understood what needed to be done. However, I would love to be mentored on it since it would be a more correct solution, and I can learn more about how bootstrap works.

Author: matthiaskrgr

src/bootstrap/check.rs

@@ -140,7 +140,13 @@ impl Step for Std {
             cargo_subcommand(builder.kind),
         );
 
-        cargo.arg("--all-targets");
+        // If we're not in stage 0, tests and examples will fail to compile
+        // from `core` definitions being loaded from two different `libcore`
+        // .rmeta and .rlib files.
+        if compiler.stage == 0 {
+            cargo.arg("--all-targets");
+        }
+
         std_cargo(builder, target, compiler.stage, &mut cargo);
 
         // Explicitly pass -p for all dependencies krates -- this will force cargo