Support for the ARM 64 bit CPU architecture (aarch64) was introduced in autoconf 2.69. glib 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/glib/glib-aarch64.patch which updates config.guess and config.sub to recognize aarch64.
The glib package is long dead upstream, so any support for this needs to happen downstream. In fact, it should already work, because the glib build copies config.sub and config.guess from /usr/lib/rpm before running configure - this was added way back for x86_64 support. Since the versions of config.sub and config.guess in /usr/lib/rpm in both F-19 and Rawhide include aarch64 support, I believe nothing needs to be done to have working aarch64 support.
There is things that need to be done. The way to tell if it supports aarch64 is to grep the config.guess file for that string. Doing a "fedpkg prep" shows this. You also use autoconf-2.13 where as aarch64 support wasn't added until 2.69 so you do need to apply this patch. Also the shipped config.guess don't appear to have been regenerated with the new autoconf for aarch64, that's a separate bug I'll file.
I did a fedpkg prep and grepped for aarch64 in config.sub and config.guess - it was present in both files (no patch needed). What more needs to be done? The supplied patch only touches config.guess and config.sub; why would using that work better than copying them in from /usr/lib/rpm as at present?
Nothing needs to be done here. Your package uses %configure macro which solves this automatically (bug #951442). Pavel