add stub for retrieving number of CPUs

src/librustc_back/target/l4re_base.rs

@@ -34,7 +34,7 @@ pub fn opts() -> TargetOptions {
         has_elf_tls: false,
         exe_allocation_crate: None,
         panic_strategy: PanicStrategy::Abort,
-        linker: "ld".to_string(),
+        linker: Some("ld".to_string()),
         pre_link_args: args,
         target_family: Some("unix".to_string()),
         .. Default::default()

src/libtest/lib.rs

@@ -1294,6 +1294,12 @@ fn get_concurrency() -> usize {
         // FIXME: implement
         1
     }
+
+    #[cfg(target_os = "l4re")]
+    fn num_cpus() -> usize {
+        // FIXME: implement
+        1
+    }
 }
 
 pub fn filter_tests(opts: &TestOpts, tests: Vec<TestDescAndFn>) -> Vec<TestDescAndFn> {