Add a quick sanity check here. The binary could have been moved or the

permissions changed which would cause the following grep for mos_so to
fail which then resulted in a misleading error message being printed.
We might also want to check for people who do ./configure --prefix=.
and disallow it or replace it with the absolute path to the current dir
since a $CFG_SBINDIR for ./bin in apxs doesn't make any sense.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@82909 13f79535-47bb-0310-9956-ffa450edef68