The latest version of GPRbuild has been built for F24 and Rawhide on ppc64, ppc64le, s390x and aarch64, and has successfully rebuilt itself and XMLada in Koji. Thus all Ada packages should now be buildable on all of these architectures. Today an update has been pushed to testing for the primary architectures to synchronize the release numbers across all the architectures.
If builds keep failing, then please ensure that gprbuild-2015-13 is in the buildroot, not some lower-numbered version that was shadow-built more recently.
This GPRbuild is statically linked so that future version upgrades should go more smoothly.
As Adacore usually publish new releases of all their packages at once, it's important to note for the future that a new version of XMLada should be built first, and be present in the build root when the new GPRbuild is built. Otherwise the old XMLada will get statically linked into GPRbuild. I suspect that Koji-shadow might not take care of this automatically.
In F23 the situation is still unresolved. Progress is hampered by what looks like a compiler bug that manifests only in recent GCC 5 versions on armv7hl.
Björn Persson