note that -j is not supported on buildroot.
it is used however internally to use by default all your processors when compiling, so, just don't care about -j.
however, you'll get the same error ;-)
we've upgraded a lot of things and some boards, like the odroid xu4 are still broken. i've to fix it. that's unfortunaltly not the only package not working on odroid xu4.
Just way or build an other target