vineyard: try to debug macos test failure

Follow-up to #230431

Author: carlocab

Formula/v/vineyard.rb

@@ -149,7 +149,8 @@ def install
 
     # sleep to let vineyardd get its wits about it
     sleep 10
-    sleep 10 if OS.mac? && Hardware::CPU.intel?
+
+    assert_predicate testpath/"vineyard.sock", :socket?
 
     assert_equal("vineyard instance is: 0\n",
                  shell_output("#{testpath}/build/vineyard-test #{testpath}/vineyard.sock"))