Zuul: Unify all jobs to save on CI costs

We need a VM for both the compose-dry-run and the compose-base tests
thus to avoid spawning two VMs in Zuul, let's keep everything in a
single job to save money.

.zuul.yaml

@@ -2,26 +2,13 @@
      check:
        jobs:
          - validate
-         - compose-base
 
  - job:
      name: validate
-     description: Validate manifests and scripts syntax
-     run: ci/validate.yaml
-     nodeset:
-       nodes:
-         - name: container
-           # Replace by a fixed version label after branching, once available:
-           # https://fedora.softwarefactory-project.io/zuul/labels
-           # The Rawhide container is temporarily broken
-           # label: zuul-worker-rawhide
-           label: cloud-fedora-rawhide-small
-
- - job:
-     name: compose-base
-     description: Test composing the base variant
+     description: Validate manifests, scripts, dependencies and compose the base image
+     # Increased timeout as builds can take a while
      timeout: 3600
-     run: ci/compose-base.yaml
+     run: ci/validate.yaml
      nodeset:
        nodes:
          - name: vm

ci/compose-base.yaml

@@ -1,17 +0,0 @@
- - hosts: all
-   tasks:
-     - name: Install dependencies
-       package:
-         name:
-           - 'jq'
-           - 'just'
-           - 'ostree'
-           - 'python3-pyyaml'
-           - 'rpm-ostree'
-           - 'selinux-policy-targeted'
-         state: present
-       become: yes
-     - name: Compose the base variant
-       ansible.builtin.command:
-         chdir: "{{ zuul.project.src_dir }}"
-         cmd: just compose-legacy base

ci/validate.yaml

@@ -3,10 +3,12 @@
      - name: Install dependencies
        package:
          name:
+           - 'jq'
            - 'just'
            - 'ostree'
            - 'python3-pyyaml'
            - 'rpm-ostree'
+           - 'selinux-policy-targeted'
          state: present
        become: yes
      - name: Validate manifests and scripts syntax
@@ -17,3 +19,7 @@
        ansible.builtin.command:
          chdir: "{{ zuul.project.src_dir }}"
          cmd: just compose-dry-run
+     - name: Compose the base variant
+       ansible.builtin.command:
+         chdir: "{{ zuul.project.src_dir }}"
+         cmd: just compose-legacy base