autobuild: Use cp --recursive --link --archive

autobuild: Use cp --recursive --link --archive

This works on waf based builds as source files are not modified during the build

TODO: In order to make sure build doesn't influence each other,
we need to add something like:

         try:
             if options.rebase is not None:
                 rebase_tree(options.rebase, rebase_branch=options.branch)
+            run_cmd("find -type f | xargs chmod -w", show=True, dir=test_master)
         except Exception:

But that means we need to change the way 'make distcheck' works for the
standalone libraries.

For now this will help to reduce the (mem)disk usage of an autobuild a lot.

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Stefan Metzmacher <metze@samba.org>