Starting with root 6.08, it was possible to build root on aarch64 and run the test suite. And up until January root built without problems in Fedora's package build system (koji) for this architecture. Then something happened and it stopped working. Even rebuilding the same version on a stable release such as RHEL/EPEL 7 that previously worked started failing.
I reported this to those responsible for running the build system:
It is not clear what exactly is causing the problem, but since the aarch64 builds last succeeded the VMs on which the build system is running were upgraded from Fedora 24 to Fedora 25. This could mean that there are new features in the aarch64 that affect the builds.
During the failing builds the compilation itself works fine, it is when the build is trying to run the newly built binaries it fails - which first happens when the hsimple.C is executed to create hsimple.root - and segfaults.
The latest comment on the above mentioned Fedora ticket asked whether all aarch64 specific fixes have been ported to the bundled llvm/cling in root. Are you aware of something not yet included in root's llvm that could cause these issues?