mgen build was spectacularly broken, not even being cross-compiled for the
target, fix that and make sure that we use the toolchain binaries were
relevant.
Signed-off-by: Florian Fainelli <florian@openwrt.org>
git-svn-id: svn://svn.openwrt.org/openwrt/packages@39813 3c298f89-4303-0410-b956-a3cf2f4a3e73