Hello,
In mono I used to have this in the SPEC file: ExclusiveArch: %mono_arches
I am not aware of something that already exits for .NET, but that's a good idea. We should investigate this for .NET.
For mono, those arches are defined in this file: https://src.fedoraproject.org/rpms/redhat-rpm-config/blob/rawhide/f/macros.m...
# arches that mono builds on %mono_arches %{ix86} x86_64 sparc sparcv9 ia64 %{arm} aarch64 alpha s390x ppc ppc64 ppc64le
all the best, Timotheus