i did change the repo url to a german one, and it’s better like that.
it is gcc5 in the 16.10 xubuntu machine, and the error seems known U-boot compilation error
i ll try to fix it
edit:
sudo apt-get install libnewlib-arm-none-eabi
did fix the issue!
and I now have managed to build another image on a second (and faster) computer;
this image boots ok