dpkg: modify the run-postinst script to enable postinst logging
Enable postinst logging by checking the configuration in ${sysconfdir}
/default/postinst.
In this way, the postinst logging is enabled if 'debug-tweaks' is
in IMAGE_FEATURES, and at the same time, we avoid unnecessary rebuilt
if IMAGE_FEATURES is changed.
[YOCTO #4262]
Signed-off-by: Chen Qi <Qi.Chen@windriver.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
