Support for the ARM 64 bit CPU architecture (aarch64) was introduced in autoconf 2.69. atf 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/atf/atf-aarch64.patch which updates config.guess and config.sub to recognize aarch64.
Have you built and run the test suite successfully after the above steps? I'm wondering if there are any other fixes to be made for aarch64. At the moment I don't have any substantial changes in the pipeline to warrant a new release of ATF, so I might go for option 2 instead temporarily. Thanks.