Also (re-)adds some debian armhf-patches – not really needed, but making
it easier to apply the libstdc++-related patches without having to
modify them.
Switching to an Arch based build process for easier maintenance and
using specific runners for tasks where that might be necessary.
Right now, parent/child pipelines for somewhat parallel builds for
different architectures / semi-independent pak-builds don't seem to
properly work yet due to `trigger:` not being recognized when it should,
so that's not yet implemented.
