test-devcontainer: Build image before testing

The test was pulling pre-built images from the registry, but those
don't have the selftest script until this PR is merged. Build the
image locally first using the existing just targets.

Also switch from docker to podman for consistency with the build.

Author: cgwalters

.github/workflows/test-devcontainer.yml

@@ -27,12 +27,8 @@ jobs:
       - name: Set up runner
         uses: bootc-dev/actions/bootc-ubuntu-setup@main
 
-      - name: Login to GitHub Container Registry
-        uses: docker/login-action@v3
-        with:
-          registry: ${{ env.REGISTRY }}
-          username: ${{ github.repository_owner }}
-          password: ${{ secrets.GITHUB_TOKEN }}
+      - name: Build devcontainer image
+        run: just devenv-build-${{ matrix.os }}
 
       - name: Test nested podman in devcontainer
-        run: just devcontainer-test ${{ env.REGISTRY }}/${{ github.repository_owner }}/devenv-${{ matrix.os }}:latest
+        run: just devcontainer-test localhost/bootc-devenv-${{ matrix.os }}:latest

Justfile

@@ -15,7 +15,6 @@ devenv-build: devenv-build-debian
 
 # Test nested podman and VMs work in a devcontainer image
 # Usage: just devcontainer-test <image>
-# Example: just devcontainer-test ghcr.io/bootc-dev/devenv-debian:latest
-# Note: Uses --privileged because Docker doesn't support podman's unmask=/proc/* option
+# Example: just devcontainer-test localhost/bootc-devenv-debian:latest
 devcontainer-test image:
-	docker run --rm --privileged "{{ image }}" /usr/libexec/devenv-selftest.sh
+	podman run --rm --privileged "{{ image }}" /usr/libexec/devenv-selftest.sh