Ensure parent directories are created for base boxes

post-processor/vagrant/util.go

@@ -39,6 +39,13 @@ func CopyContents(dst, src string) error {
 // actually a proper box. This is an expected precondition.
 func DirToBox(dst, dir string, ui packer.Ui, level int) error {
 	log.Printf("Turning dir into box: %s => %s", dir, dst)
+
+	// Make the containing directory, if it does not already exist
+	err := os.MkdirAll(filepath.Dir(dst), 0755)
+	if err != nil {
+		return err
+	}
+
 	dstF, err := os.Create(dst)
 	if err != nil {
 		return err