meta/classes/sstate.bbclass: ensure sstate files have group R/W

In order to make sharing sstate files easier chmod them with 0664 permissions	so that they are readable and writable by the user and any other members of 	their group.

(From OE-Core rev: dae9ad8a0ba0343e3083694cdcb20f0d02927ad0)

Signed-off-by: Joshua Lock <josh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

meta/classes/sstate.bbclass

@@ -473,6 +473,7 @@ sstate_create_package () {
 	else
 		tar -cz --file=$TFILE --files-from=/dev/null
 	fi
+	chmod 0664 $TFILE 
 	mv $TFILE ${SSTATE_PKG}
 
 	cd ${WORKDIR}