config.gcc (i[34567]86-*-pe|i[34567]86-*-cygwin*): Specify extra host object file when targetting cygwin.

* config.gcc (i[34567]86-*-pe|i[34567]86-*-cygwin*): Specify extra host object
file when targetting cygwin.
* config/i386/t-cygwin (EXTRA_GCC_OBJS): Remove definition since it is
overridden by top-level Makefile.

From-SVN: r78241