@suzuke i've tested n64 without success. i've not searched the cause.
for the xu4, i've merged buildroot 2017/12 to a branch called xu4-414. i've fixed upgrade issues for x86 and rpi.
now, i will merge this branch in the master, so possibly it may break some things for the s905, or cause minor conflicts (you'll have to rebase).
i do this merge now because i would like to release a new version at the end of the month, at least for rpi while amiga is ready from a long time and kodi is upgraded to 17.6.
possibly i will not release version for xu4 while i've still one unfixed bug.
for s905, i may reread your work and merge it soon too if you want.
my message is not clear at all, but just remember there will have movement on the master branch and that i hope a rebase will not conflit too much for you.