Support for the ARM 64 bit CPU architecture (aarch64) was introduced in autoconf 2.69. valgrind 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/valgrind/valgrind-aarch64.patch which updates config.guess and config.sub to recognize aarch64.
That looks pretty much as a useless patch, valgrind would need an aarch64 port first, which is several months of work usually.
I agree with Jakub. This doesn't make any sense unless someone is writing an ARM64 port. I don't know about anybody working on it upstream. Lets close till that happens.