Fix out of tree build with srclib apr.

Fix error message for included apr flag.

Forward port of r1241897 and r1243670
from 2.4.x plus one shell syntax fix.

Will backport the fix to 2.4.x.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1243797 13f79535-47bb-0310-9956-ffa450edef68