hg: bsd-port/jdk8: Use a more reliable method for checking if -z wxneeded is supported

[kurt at intricatesoftware.com]

Changeset: 7d10cb157877
Author:    Kurt Miller <kurt at intricatesoftware.com>
Date:      2019-01-22 15:36 -0500
URL:       http://hg.openjdk.java.net/bsd-port/jdk8/rev/7d10cb157877

Use a more reliable method for checking if -z wxneeded is supported
by ld on OpenBSD.

! common/autoconf/generated-configure.sh
! common/autoconf/toolchain.m4