Store nix version in common config file

archiso/scripts/build.fish

@@ -1,6 +1,6 @@
 #!/bin/env fish
 begin
-    set -l nixVersion nixos-24.05
+    source "$(status dirname)/../../scripts/config.fish"
     set -l projectName archiso-valhalla
     set -l overlayDir (mktemp -d)
     set -l upperDir (mktemp -d)

scripts/Common/OS/install.fish

@@ -5,7 +5,7 @@ source "$dir/../Scripts/settings.fish"
 source "$dir/../Scripts/hooks.fish"
 
 if [ (id -u) -eq 0 ]
-    set -l nixVersion nixos-24.05
+    source "$dir/../../config.fish"
     set -l sudoConfig "/etc/sudoers.d/PortValhalla"
     set -l channelDir /nix/var/nix/profiles/per-user/root/channels/nixpkgs
     rm ~/.bash_profile

scripts/config.fish

@@ -0,0 +1 @@
+set nixVersion nixos-24.05