nix: Move unfree allowing into os config

Might need the same for HM config?

config/nix/build-pindakaas-image.sh

@@ -7,7 +7,6 @@ then
     exec nix-shell -p nix-output-monitor --run $0
 fi
 
-export NIXPKGS_ALLOW_UNFREE=1
 extra=""
 if [ "$(uname -m)" != "aarch64" ]
 then

config/nix/build-vm.sh

@@ -10,7 +10,6 @@ then
     exec nix-shell -p nix-output-monitor --run $0
 fi
 
-export NIXPKGS_ALLOW_UNFREE=1
 if [ "$(uname -m)" == "x86_64" ]
 then
     config=./curacao.nix

config/nix/os/common.nix

@@ -30,6 +30,8 @@
     android-udev-rules
   ];
 
+  nixpkgs.config.allowUnfree = true;
+
   programs = {
     # Enable compilation cache
     ccache.enable = true;