Creates a symbolic link. Returns a Future<Link> that completes with
the link when it has been created. If the link exists,
the future will complete with an error.
If recursive is false, the default, the link is created
only if all directories in its path exist.
If recursive is true, all non-existing path
components are created. The directories in the path of target are
not affected, unless they are also in path.
On the Windows platform, this call will create a true symbolic link
instead of a Junction. In order to create a symbolic link on Windows, Dart
must be run in Administrator mode or the system must have Developer Mode
enabled, otherwise a FileSystemException will be raised with
ERROR_PRIVILEGE_NOT_HELD set as the errno when this call is made.
On other platforms, the posix symlink() call is used to make a symbolic
link containing the string target. If target is a relative path,
it will be interpreted relative to the directory containing the link.
Future<Link> create(String target, {bool recursive: false});