systemd: add shell-profile-dropins PACKAGECONFIG

systemd: add shell-profile-dropins PACKAGECONFIG

New version of systemd introduces dropins in /etc/profile.d. This
is usually OK for most cases. But in case of using minicom to connect
to the machine, there will be unnecessary output every time you type
a command.

This is because the /etc/profile.d/80-systemd-osc-context.sh[1] is setting
PS0 with OSC 3008 standard[2]. If a terminal (e.g., minicom) cannot
deal with this OSC 3008 standard, it will just output the whole contents.
This is quite annoying.

So add a new PACKAGECONFIG, shell-profile-dropins, to allow users a choice
to disable such behavior.

[1] https://github.com/systemd/systemd/commit/dadbb34919abd3fefeb5b8ccc9794da9398a2503
[2] https://uapi-group.org/specifications/specs/osc_context/

Signed-off-by: Chen Qi <Qi.Chen@windriver.com>
Signed-off-by: Antonin Godard <antonin.godard@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>