gdb/systemd: enable minidebuginfo support conditionally

gdb/systemd: enable minidebuginfo support conditionally

Enabling minidebuginfo is not useful if gdb and systemd-coredump
are unable to parse it.

In order to parse it, gdb needs xz support. Systemd needs coredump enabled, as
well as elfutil enabled as well (systemd-coredump loads libdw which is part of elfutils using dlopen).

Signed-off-by: Etienne Cordonnier <ecordonnier@snap.com>
Signed-off-by: Alexandre Belloni <alexandre.belloni@bootlin.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>