Support for the ARM 64 bit CPU architecture (aarch64) was introduced in autoconf 2.69. mod_gnutls 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/mod_gnutls/mod_gnutls-aarch64.patch which updates config.guess and config.sub to recognize aarch64.
autoreconf is called before configure, created bug: https://sourceforge.net/apps/mantisbt/mod-gnutls/view.php?id=18
mod_gnutls site moved to mod.gnutls.org, new tracker is https://mod.gnutls.org/ticket/18