CI: ubuntu needs to explicitly install Ninja

.github/workflows/nightly-ubuntu.yml

@@ -25,7 +25,7 @@ jobs:
         shell: bash
         run: |
             apt-get update
-            apt-get -y install git-core jq curl
+            apt-get -y install git-core jq curl ninja-build
       - name: "prepare source"
         uses: calamares/actions/generic-checkout@v5
       - name: "install dependencies"