Tweak the logic to avoid "make distclean" inside APR directories so that

it works on Tru64.  On that platform, when grep failed (because we weren't
in an APR directory), the non-zero exit status failed the entire operation.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@87096 13f79535-47bb-0310-9956-ffa450edef68