feat: update build process to use NixOS environment with Buildah and Podman

Signed-off-by: Uwe Hermann <uh@uleenucks.de>

.gitea/workflows/test_build_and_push.yaml

@@ -20,7 +20,8 @@ jobs:
   buildpush:
     name: build_and_push
     needs: [test_shellcheck]
-    runs-on: ubuntu-latest
+    runs-on: [self-hosted, nixos]  # For NixOS runners
+    # runs-on: ubuntu-latest     # For Ubuntu runners
     strategy:
       matrix:
         image:
@@ -37,6 +38,16 @@ jobs:
     steps:
       - uses: actions/checkout@v4
 
+      - name: Setup NixOS environment
+        run: |
+          # Ensure buildah and podman are available
+          export PATH="/run/wrappers/bin:/run/current-system/sw/bin:/nix/var/nix/profiles/default/bin:$PATH"
+          echo "PATH=$PATH" >> $GITHUB_ENV
+          
+          # Verify tools are available
+          which buildah || echo "buildah not found in PATH"
+          which podman || echo "podman not found in PATH"
+
       - name: Build ${{ matrix.image.name }} image
         id: build
         uses: redhat-actions/buildah-build@v2