string is not allowed to refer to a store path

[raboof]

When I make upstaisr image=phramware on NixOS unstable, I get the above error about a string containing a lot of config settings, including:

 "CONFIG_SHELL": "/nix/store/wadmyilr414n7bimxysbny876i2vlm5r-bash-5.1-p8/bin/bash"

That shell does exist on my machine, but isn't the one I'm using - not sure where that comes from.

The full output (with trace) is out.txt

Replacing the two occurances of type -p bash in nixwrt/kernel/make-backport-modules.nix is not sufficient - somehow CONFIG_SHELL comes pre-populated when creating defconfig.json in nixwrt/kernel/default.nix (even before source ${file}) - though I don't understand where that's coming from.