Support for the ARM 64 bit CPU architecture (aarch64) was introduced in autoconf 2.69. pam_ldap appears to use an earlier version of autoconf, preventing its being built. This can be fixed in of three ways (In order of preference): 1. Work with upstream to migrate the package to autoconf 2.69. 2. Rerun autoconf or autoreconf in %prep or %build prior to running configure. 3. Apply the patch at http://ausil.fedorapeople.org/aarch64/pam_ldap/pam_ldap-aarch64.patch which updates config.guess and config.sub to recognize aarch64.
pam_ldap's not supposed to be in F19 or later. Marking won't-fix because we won't be fixing this.