Comment # 5 on bug 1127769 from Michael Schr�der

There's a hack in newer(!) rpm versions that allows to use ExclusiveArch for
noarch packages (without this hack the construct would not make sense at all,
because after the "BuildArch: noarch" the architecture is always "noarch".

Unfortunately rpm does not canonicalize the architecture in that case, so you
get a weird architecture like "powerpc64le". This may be considered a bug that
needs to be fixed.