Refresh namespace runtime config and linux nix env

.forgejo/workflows/build-site.yml

@@ -17,6 +17,10 @@ jobs:
   site:
     name: Next.js Build
     runs-on: namespace-profile-linux-medium
+    env:
+      NIX_CONFIG: |
+        experimental-features = nix-command flakes
+        accept-flake-config = true
     steps:
       - name: Checkout
         uses: https://code.forgejo.org/actions/checkout@v4
@@ -38,6 +42,11 @@ jobs:
           echo "NPM_CONFIG_CACHE=${shared_root}/npm" >> "${GITHUB_ENV}"
           echo "XDG_CACHE_HOME=${shared_root}/xdg" >> "${GITHUB_ENV}"
           echo "NEXT_CACHE_DIR=${lane_root}/next-cache" >> "${GITHUB_ENV}"
+          {
+            echo 'NIX_CONFIG<<EOF'
+            printf '%s\n' "${NIX_CONFIG}"
+            echo 'EOF'
+          } >> "${GITHUB_ENV}"
           df -h /nix "${shared_root}" "${lane_root}" || true
 
       - name: Build