OS/390: avoid unconditional -ldl and -export-dynamic (other

platforms can add related logic to the case statement)

This is a stop-gap measure until the need for certain libraries
can be determined automatically.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@85448 13f79535-47bb-0310-9956-ffa450edef68