fix: explicitly add nix bin to PATH after sourcing nix.sh in Docker

iso/_inner-build-live.sh

@@ -69,7 +69,9 @@ if [[ -n "${NIX_PACKAGES_PREBAKE:-}" ]]; then
         curl -fsSL https://nixos.org/nix/install | \
             NIX_INSTALLER_TRUST_INSTALLER=1 sh -s -- --no-daemon --no-channel-add
         # shellcheck disable=SC1091
-        . /root/.nix-profile/etc/profile.d/nix.sh
+        . /root/.nix-profile/etc/profile.d/nix.sh 2>/dev/null || true
+        # Explicitly add nix to PATH in case the profile script didn't export it
+        export PATH="/root/.nix-profile/bin:/nix/var/nix/profiles/default/bin:$PATH"
 
         export NIXPKGS_ALLOW_UNFREE=1
         echo "    nix profile install: ${_NIX_PKGS[*]}"