Explicitly list in which directories to look for config*.m4 files.

If some distributor patches a config*.m4 file with quilt, that will
place a copy of the original file in .pc/ . Doing a naive "find ."
will then cause both the original and the patched m4 file to be included,
causing havoc later on.

PR: 55787


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1542615 13f79535-47bb-0310-9956-ffa450edef68