actions: split build and test jobs

.github/workflows/test-build.yml

@@ -5,8 +5,38 @@ concurrency:
   group: "${{ github.ref }}"
   cancel-in-progress: true
 jobs:
+  build-debian:
+    strategy:
+      # Keep other matrix jobs running, even if one fails.
+      fail-fast: false
+      matrix:
+        host_release:
+        - unstable
+        - trixie
+        - bookworm
+        - bullseye
+
+    # We want a working shell, qemu, python and docker. Specific version should not matter (much).
+    runs-on: ubuntu-latest
+
+    steps:
+    - uses: actions/checkout@v4
+
+    - run: ./tests/gha-build-deb.sh
+      name: "Build .deb for ${{matrix.host_release}}"
+      env:
+        HOST_RELEASE: ${{matrix.host_release}}
+
+    - name: Archive built .deb
+      uses: actions/upload-artifact@v3
+      with:
+        name: deb-${{matrix.host_release}}
+        if-no-files-found: error
+        path: |
+          *.deb
 
-  debian:
+  test-debian:
+    needs: build-debian
     strategy:
       # Keep other matrix jobs running, even if one fails.
       fail-fast: false
@@ -38,10 +68,10 @@ jobs:
     steps:
     - uses: actions/checkout@v4
 
-    - run: ./tests/gha-build-deb.sh
-      name: "Build .deb for ${{matrix.host_release}}"
-      env:
-        HOST_RELEASE: ${{matrix.host_release}}
+    - name: Download built deb
+      uses: actions/download-artifact@v3
+      with:
+        name: deb-${{matrix.host_release}}
 
     - run: ./tests/build-vm-and-test.sh setup
       name: "Setup test environment"
@@ -58,14 +88,6 @@ jobs:
       env:
         RELEASE: ${{matrix.release}}
 
-    - name: Archive built .deb
-      uses: actions/upload-artifact@v3
-      with:
-        name: deb-${{matrix.host_release}}
-        if-no-files-found: error
-        path: |
-          *.deb
-
     - name: Archive VM test results
       uses: actions/upload-artifact@v3
       with: