[OE-core] dora: systemd + package_deb = broken run-postinsts

[Steve Sakoman]

A client has requested help setting up a build using debian packaging
and systemd as the init system.

When testing the initial image build I noticed that package postinsts
didn't seem to run properly.

It turns out that dpkg installs an S98run-postinsts file in /etc/rcS.d
in addition to the normal S99run-postinsts link to
/etc/init.d/run-postinsts.

Systemd-compat-units installs a run-postinsts.service file that calls
/etc/rcS.d/S99run-postinsts.

I haven't investigated why the standard /etc/rcS.d/S99run-postinsts
doesn't work properly for the debian case, but I have verified that
changing the service file to use the dpkg provided
/etc/rcS.d/S98run-postinsts works, as does changing dpkg to write
S99run-postinsts instead of S98run-postinsts.

I'm not sure what the "proper" fix is for this issue.  Any
debian/systemd experts care to weigh in with advice?

Regards,

Steve