[fix] don't panic on failure to acquire jobserver token

compiler/rustc_codegen_ssa/src/back/write.rs

@@ -1452,8 +1452,8 @@ fn start_executing_work<B: ExtraBackendMethods>(
                         Err(e) => {
                             let msg = &format!("failed to acquire jobserver token: {}", e);
                             shared_emitter.fatal(msg);
-                            // Exit the coordinator thread
-                            panic!("{}", msg)
+                            codegen_done = true;
+                            codegen_aborted = true;
                         }
                     }
                 }