While resolving the path, the last step will reduce it down to ""
(an empty string) and realpath() will resolve this to getcwd().
If open_basedir contains the CWD, then that means open_basedir
will be bypassed for paths that don't have any components that
exist (if one of the components exists, then we abort the realpath
loop at that point).
Closes GH-7015.
Nikita Popov
ee7a8acde9