lib/oe/path: Fix performance issue got copyhardlinktree()

lib/oe/path: Fix performance issue got copyhardlinktree()

With the directory copy was added to avoid race issues, it wasn't noticed that
tar was recursing the directories and copying files too. This is completely
crazy when we hardlink those files in the next command.

Resolve the issue by telling tar not to recurse. This gives a significant
performance boost to various parts of the system (do_package for linux-yocto
256s -> 178s for example).

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>