sftp: add required packages to vendor

vendor/github.com/pkg/sftp/attrs_unix.go

@@ -0,0 +1,17 @@
+// +build darwin dragonfly freebsd !android,linux netbsd openbsd solaris
+// +build cgo
+
+package sftp
+
+import (
+	"os"
+	"syscall"
+)
+
+func fileStatFromInfoOs(fi os.FileInfo, flags *uint32, fileStat *FileStat) {
+	if statt, ok := fi.Sys().(*syscall.Stat_t); ok {
+		*flags |= ssh_FILEXFER_ATTR_UIDGID
+		fileStat.UID = statt.Uid
+		fileStat.GID = statt.Gid
+	}
+}