Add correct build value for cross-compiled targets on stage1 when
bootstapping rustc.

Upstream-Status: Backport [https://github.com/rust-lang/rust/pull/119619/commits/b888e2f82b9dbe81875f50d13adbc0271a9401ff]

Signed-off-by: onur-ozkan <work@onurozkan.dev>
Signed-off-by: Yash Shinde <Yash.Shinde@windriver.com>
---
diff --git a/src/bootstrap/test.rs b/src/bootstrap/test.rs
--- a/src/bootstrap/src/core/build_steps/test.rs
+++ b/src/bootstrap/src/core/build_steps/test.rs
@@ -1489,8 +1489,12 @@
         // NOTE: Only stage 1 is special cased because we need the rustc_private artifacts to match the
         // running compiler in stage 2 when plugins run.
         let stage_id = if suite == "ui-fulldeps" && compiler.stage == 1 {
-            compiler = builder.compiler(compiler.stage - 1, target);
-            format!("stage{}-{}", compiler.stage + 1, target)
+            // At stage 0 (stage - 1) we are using the beta compiler. Using `self.target` can lead finding
+            // an incorrect compiler path on cross-targets, as the stage 0 beta compiler is always equal
+            // to `build.build` in the configuration.
+            let build = builder.build.build;
+            compiler = builder.compiler(compiler.stage - 1, build);
+            format!("stage{}-{}", compiler.stage + 1, build)
         } else {
             format!("stage{}-{}", compiler.stage, target)
         };