Description of problem:
The spec file contains an error, it lists --with-apxs=/usr instead of
--with-apache=/usr

This cause a build as user using a command like this:
rpmbuild --define "_topdir /my/own/rpmbuild/tree" -ba mod_auth_kerb.spec
to fail.
The reason it works normally is that when built as root '/usr/sbin' is in the
path so the configure finds it. When building as user '/usr/sbin' is not in the
path by default and configure fails to find apxs

Version-Release number of selected component (if applicable):
5.3-*

Additional info:

The fix is simple, use --with-apache=/usr and not --with-apxs=/usr (--with-apxs
is something unknown to the configure.in file).