resolv.conf always empty

I have 2 different embedded devices…an old one running TI arago Linux and a Xilinx device (petalinux).

On both I see the same outcome when adding dns-nameservers to /etc/network/interfaces and reconfiguring the network with /etc/init.d/networking restart or rebooting the device:
The /etc/resolv.conf file always stays empty.

No dhclient, resolvconf package, network-manager daemon or mdns are present in the system.

Here the /etc/network/interfaces:

# /etc/network/interfaces -- configuration file for ifup(8), ifdown(8)

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
    address 192.168.1.2
    netmask 255.255.255.0
    gateway 192.168.1.1
    dns-nameservers 192.168.1.1

and resolv.conf:

[root@linux:~] ls -l /etc/resolv.conf 
lrwxrwxrwx    1 root     root           20 Feb  3 18:17 /etc/resolv.conf -> /var/run/resolv.conf
[root@linux:~] ls -l /var/run/resolv.conf
-rw-r--r--    1 root     root            0 Feb  3 18:17 /var/run/resolv.conf

While executing /etc/init.d/networking restart, both devices call basically ifdown -a and then ifup -a, being both ifup and ifdown busybox utilities in this case.

In case mentioning the immutable file attributes solution: I don’t want to generate manually the resolv.conf file and change the file attributes to make it immutable (chattr +i), because it seems completely against how the system was designed. Why is then resolv.conf stored in volatile memory (generated by populate-volatile.sh) in the first place, if it should be permanent?

Thanks for any hints!

Update: found the solution, but will leave the question, for the sake of somebody searching for it.

#!/bin/sh
if [ "$IFACE" = "eth0" ];then
for NS in $IF_DNS_NAMESERVERS; do
R="${R}nameserver $NS
"
done
echo "$R" > /etc/resolv.conf
fi