chmod +x $out/etc/init.d/... not working

[GrumpyMeow]

With this perfect, great builder i'm able to initialize, upgrade and provision my router and access points in a matter of minutes. I love it!
I've created a dozen of nix-files which results in installing packages and provisioning uci-defaults files to do all the configuration.
For each OpenWRT-device i do some concatenation like:

        ...
        luci = import ../../modules/openwrt/luci.nix;
        wpad = import ../../modules/openwrt/wpad.nix;
        iperf3 = import ../../modules/openwrt/iperf3.nix;
        watchcat = import ../../modules/openwrt/watchcat.nix;

        config = profiles.identifyProfile "ubnt_unifiac-mesh" // {

          packages = unregulatory.packages ++ zabbix_agentd.packages ++ ttyd.packages ++ usteer.packages ++ dropbear.packages ++ dumbap.packages ++ 
                     luci.packages ++ watchcat.packages ++ wpad.packages ++ iperf3.packages ++ [
            "nano"
          ];
          release = vars.openwrt.release;
          target = "ath79";
          variant = "generic";
          profile = "ubnt_unifiac-mesh";
          EXTRA_IMAGE_NAME = "ap-buiten";
          disabledServices = [ "dnsmasq" "firewall" "odhcpd" ];

          files = pkgs.runCommand "image-files" { } ''

            ${dumbap.snippet}
            ${iperf3.snippet}
            ${luci.snippet}
            ...

One small issue i seem to be running into is that i seem to be unable to get provisioned files to have the executable flag set in the resulting sysupgrade image.
Given the below nix-file which is to enable iperf3 running as a service on all my OpenWRT devices which i have Zabbix configured to test on a regular basis. It exposes a combination of packages and snippet which get concatenated with other nix-files (see the snippet above).

In this specific nix-file i write a service-definition file $out/etc/init.d/iperf3 which needs to be executable. If i add an instruction to add the executable flag on this file, the flag seems to get lost somewhere. I can imagine that this happens during the copying of files to the image.
I can workaround the issue by adding the executable flag from within a uci-defaults file. Which is not a problem, but is not as "clean" as it could be.

let
in
{
  packages = [ "iperf3" ];
  
  snippet = ''
    mkdir -p $out/etc/uci-defaults

    cat > $out/etc/uci-defaults/96-iperf3 <<EOF
     chmod +x /etc/init.d/iperf3       <=== this action does work
     /etc/init.d/iperf3 enable
     /etc/init.d/iperf3 start
EOF

    mkdir -p $out/etc/init.d

    cat > $out/etc/init.d/iperf3 <<EOF
#!/bin/sh /etc/rc.common
# Copyright (C) 2008-2011 OpenWrt.org
START=60
USE_PROCD=1
PROG=/usr/bin/iperf3
start_service() {
    procd_open_instance
    procd_set_param command /usr/bin/iperf3 -s -D
    procd_set_param respawn
    procd_set_param stdout 1
    procd_set_param stderr 1
    procd_close_instance
}

EOF

     chmod +x $out/etc/init.d/iperf3         <=== this action does not work
  '';
}

Is this an issue which might be resolved?

I think i see the same issue when looking at the uci-defaults file in /rom/etc/uci-defaults:

This as my custom uci-defaults files are not executable while the OpenWRT ones are.

thanks in advance!