Ack, I think 436e980e2ed5 ("kbuild: don't hardcode depmod path") is
stable material even if it doesn't fix a bug.
Not only does the fix for that commit not make sense without the
commit in the first place, but any environment that sets depmod
somewhere else might well be an environment that still wants stable
kernels.
It may not be the traditional case, but there's little reason for the
kernel build to force that /sbin/depmod location.