This patch removes a vestige part of the Cygwin make rules
that didn't quite make it over during the flattening of the
Makefiles. In its current form, it creates a def file but
incorrectly calls it libpython$(VERSION).dll.a which
immediately gets overwritten by the next command.
Obviously, this is useless. It appears, it was useless
in the old nested Makefile structure too. :,)