ci: Refactor libvirt setup

Move libvirt installation into a parameterized input in the
bootc-ubuntu-setup action, allowing workflows to opt-in via
`libvirt: true`. This consolidates installation logic and makes
workflows cleaner by removing duplicate package installation steps.

Assisted-by: Claude Code
Signed-off-by: Colin Walters <walters@verbum.org>

.github/actions/bootc-ubuntu-setup/action.yml

@@ -1,5 +1,10 @@
 name: 'Bootc Ubuntu Setup'
 description: 'Default host setup'
+inputs:
+  libvirt:
+    description: 'Install libvirt and virtualization stack'
+    required: false
+    default: 'false'
 runs:
   using: 'composite'
   steps:
@@ -55,3 +60,10 @@ runs:
         # Suppress actually using the cache for builds running from
         # git main so that we avoid incremental compilation bugs
         lookup-only: ${{ github.ref == 'refs/heads/main' }}
+    # Install libvirt stack if requested
+    - name: Install libvirt and virtualization stack
+      if: ${{ inputs.libvirt == 'true' }}
+      shell: bash
+      run: |
+        set -eux
+        sudo apt install -y libkrb5-dev pkg-config libvirt-dev genisoimage qemu-utils qemu-kvm qemu-utils libvirt-daemon-system

.github/workflows/ci.yml

@@ -130,8 +130,8 @@ jobs:
       - uses: actions/checkout@v4
       - name: Bootc Ubuntu Setup
         uses: ./.github/actions/bootc-ubuntu-setup
-      - name: Install qemu-utils
-        run: sudo apt install -y qemu-utils
+        with:
+          libvirt: true
 
       - name: Build container and disk image
         run: |
@@ -162,12 +162,10 @@ jobs:
       - uses: actions/checkout@v4
       - name: Bootc Ubuntu Setup
         uses: ./.github/actions/bootc-ubuntu-setup
-      - name: Install deps
-        run: |
-          sudo apt-get update
-          # see https://tmt.readthedocs.io/en/stable/overview.html#install
-          sudo apt install -y libkrb5-dev pkg-config libvirt-dev genisoimage qemu-kvm qemu-utils libvirt-daemon-system just
-          pip install --user "tmt[provision-virtual]"
+        with:
+          libvirt: true
+      - name: Install tmt
+        run: pip install --user "tmt[provision-virtual]"
 
       - name: Create folder to save disk image
         run: mkdir -p target