fix(git): add vendor in .gitignore

vendor/golang.org/x/sys/unix/sockcmsg_dragonfly.go

@@ -1,16 +0,0 @@
-// Copyright 2019 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package unix
-
-// Round the length of a raw sockaddr up to align it properly.
-func cmsgAlignOf(salen int) int {
-	salign := SizeofPtr
-	if SizeofPtr == 8 && !supportsABI(_dragonflyABIChangeVersion) {
-		// 64-bit Dragonfly before the September 2019 ABI changes still requires
-		// 32-bit aligned access to network subsystem.
-		salign = 4
-	}
-	return (salen + salign - 1) & ^(salign - 1)
-}