Support for the ARM 64 bit CPU architecture (aarch64) was introduced in autoconf 2.69. audacious-plugins 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/audacious-plugins/audacious-plugins-aarch64.patch which updates config.guess and config.sub to recognize aarch64.
Fixed in Rawhide, f19 builds submitted, too (but it could be that they won't become test-updates because of other pending changes).