[oe] Adding sumtool to a JFFS2 build to speed up first boot

[Ulf Samuelsson]

Trying to solve another problem I came up with
changing IMAGE_CMD_jffs2 defined in conf/bitbake.conf
by redefining it in conf/local.conf.

During that process I noticed the "sumtool" utility
which works on the jffs2 image, doing some
bookkeeping which then does not have to be
done on the target.

I unserstand, this can speed up loading significantly.
Any reason not using this in OE?

-- 
Best Regards
Ulf Samuelsson