While working on reproducible builds for openSUSE, I found
a new class of issues that can be very hard to trace down.
You have to know that OBS builds every noarch package for every architecture,
publishes only one (the first in prj metadata), but uses all of them for
further builds in their respective architecture in OBS.

https://github.com/openSUSE/open-build-service/issues/5784

So within OBS, noarch packages are treated pretty much like
architecture-dependant packages.
Things only start to break once you use osc build or use the packages on a user
machine and your architecture is not the one listed first in `osc meta prj`

I wrote a 'noarchcheck' script that fetches noarch rpms for 2 architectures and
uses build-compare to see if they are similar.
Of 10899 total Factory source packages,
1218/3802 noarch packages did not pass that test.

Many of the diffs seem to be harmless, so I will review the diffs and file bugs
for the uglier ones and maybe file group-bugs by class of issue for the less
severe diffs.