Add needs-ar compiletest instruction

Author: GuillaumeGomez

src/tools/compiletest/src/header/needs.rs

@@ -144,6 +144,11 @@ pub(super) fn handle_needs(
             condition: config.runner.as_ref().is_some_and(|r| r.contains("wasmtime")),
             ignore_reason: "ignored when wasmtime runner is not available",
         },
+        Need {
+            name: "needs-ar",
+            condition: !config.target.contains("msvc"),
+            ignore_reason: "ignored when ar command is not available",
+        },
     ];
 
     let (name, comment) = match ln.split_once([':', ' ']) {

tests/run-make/invalid-library/rmake.rs

@@ -1,3 +1,5 @@
+//@ needs-ar
+
 use run_make_support::fs_wrapper::create_file;
 use run_make_support::{ar_command, rustc};