README.md: Add reference to meta-openembedded/meta-gnome to be put into the build's local.conf
README.md: Add reference to meta-openembedded/meta-gnome to be
put into the build's local.conf

Signed-off-by: Florin Sarbu <486fccc676e3540ad3d2f2e342359b3d1a717bab@windriver.com>

MentorEmbedded/meta-ivi