Support for the ARM 64 bit CPU architecture (aarch64) was introduced in autoconf 2.69. mysql-proxy 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/mysql-proxy/mysql-proxy-aarch64.patch which updates config.guess and config.sub to recognize aarch64.
Thanks very much for reporting this. I've rebuild the package applying your patch for Rawhide and F19 and contacted upstream concerning a migration to autoconf 2.69.
My previous comment was for a similar issue with CTPL (#925206), I'm just working on this one as well. Sorry.
The build for aarch64 exists since almost a year now. I'm sorry I forgot updating this bug accordingly.