Use get_last_sys_error() instead of get_last_rtl_error()

get_last_sys_error() already exists, so there's no need for yet
another macro that fulfills the same purpose.

Fixes #4120

Reviewed-by: Andy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/6088)

(cherry picked from commit b4c35656)