Only use repositories that begin "poky-feed". This prevents contamination with
system repositories.
It may be better to patch yum not to ever look in the system repository
locations (i.e. /etc/yum.repos.d).
 do_rootfs[recrdeptask] += "do_package_write_rpm"
 
 YUMCONF = "${IMAGE_ROOTFS}/etc/yum.conf"
-YUMARGS = "-c ${YUMCONF} --installroot ${IMAGE_ROOTFS}"
+YUMARGS = "--disablerepo=* --enablerepo=poky-feed-* --installroot ${IMAGE_ROOTFS}"
 export YUM_ARCH_FORCE = "${TARGET_ARCH}"
 
 AWKPOSTINSTSCRIPT = "${STAGING_BINDIR_NATIVE}/extract-postinst.awk"