rustbuild: fix libtest_stamp

Signed-off-by: Marc-Antoine Perennou <Marc-Antoine@Perennou.com>

src/bootstrap/builder.rs

@@ -787,7 +787,7 @@ pub fn cargo(
 
         let libtest_stamp = match cmd {
             "check" | "clippy" | "fix" => check::libtest_stamp(self, cmp, target),
-            _ => compile::libstd_stamp(self, cmp, target),
+            _ => compile::libtest_stamp(self, cmp, target),
         };
 
         let librustc_stamp = match cmd {