copy_buildsystem.py: Add a way to copy buildsystem to a directory.

This file provides a way to take bitbake and the layers in the
current build and copy them to a target specified.

Signed-off-by: Randy Witt <randy.e.witt@linux.intel.com>
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>