rpm: pull in the alternative trigger implementation in sh

From https://src.fedoraproject.org/rpms/systemd/blob/master/f/triggers.systemd.

In 12dde791 scriptlets were converted to lua.
This is not only faster and cleaner, but also avoids a nasty dependency loop:
rpm implements the lua scripting internally, so we don't need a working shell
for the scriplets. This is nice and all, but unfortunately ostree wants to
capture scriptlets and execute them at a later time and does not support lua.
So in Fedora we ended up with a revert back to a shell-based implementation
[1]. At the time I hoped this would only be a temporary workaround, but three
years later I think it's fair to assume that this will not happen any time
soon. But carrying the upstream lua version and the downstream sh version is
error prone. So let's import the other version into our tree too so that they
can be kept in sync.

[1] https://src.fedoraproject.org/rpms/systemd/c/8e6b39457b3e2660793821e0524855226e33e306