Support for the ARM 64 bit CPU architecture (aarch64) was introduced in autoconf 2.69. nautilus-search-tool 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/nautilus-search-tool/nautilus-search-tool-aarch64.patch which updates config.guess and config.sub to recognize aarch64.
autoconf is already in the %prep for this package, so the rebuild of nautilus-search-tool-0.3.0-16.fc19 and above should have fixed this issue. If not, please feel free to reopen!
Let's try proper bug workflow this time. ;-)