PX4 build for OcPoc

I am having problems with PX4 on OcPoc.

I am building on a virtual machine with Ubuntu 16.04 where I have installed the depencies with https://raw.githubusercontent.com/PX4/Devguide/master/build_scripts/ubuntu_sim.sh.

I have followed the instructions in https://aerotenna.readme.io/docs/px4-setup. Please, note that build instructions in https://aerotenna.readme.io/docs/downloading-required-files (make posix_ocpoc_ubuntu) seem to be wrong, so I built using make aerotenna_ocpoc_ubuntu (as in https://github.com/PX4/px4_user_guide/blob/master/en/flight_controller/ocpoc_zynq.md).

However, when I run px4 in Ocpoc (./px4 posix-configs/ocpoc/px4.config from /root folder) I got the following error:
root@ubuntu-armhf:~# ./px4 posix-configs/ocpoc/px4.config
INFO [px4] Creating symlink posix-configs/ocpoc/px4.config -> /root/etc
ERROR [px4] Error opening startup file, does not exist: etc/init.d/rcS

If I run px4 from / folder, I can run it but when I execute any command (such as led_control on), I get a segmentation fault:
root@ubuntu-armhf:/# /root/px4 /root/posix-configs/ocpoc/px4.config

px4 starting.

INFO [px4] Calling startup script: /bin/sh etc/init.d/rcS 0
INFO [px4] Startup script returned successfully
pxh> led_control on

Segmentation Fault
INFO [log] Backtrace: 0

On the other side, I have noticed that when I run px4 from /root folder, a link etc (in /root folder) to posix-configs/ocpoc/px4.config is generated.

It seems that there is some problem with my built, missing path or missing step in the build. Could you provide me with assistance to fix this problem?