tests: seprate core test so it uses Snapcraft 4.x

Signed-off-by: Sergio Schvezov <[email protected]>

.github/workflows/test.yml

@@ -20,7 +20,6 @@ jobs:
     strategy:
       matrix:
         project:
-          - core
           - core18
           - core20
     steps:
@@ -34,6 +33,24 @@ jobs:
         name: 'snap'
         path: ${{ steps.snapcraft.outputs.snap}}
 
+  integration-legacy: # make sure the action works on a clean machine without building
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        project:
+          - core
+    steps:
+    - uses: actions/checkout@v2
+    - uses: ./
+      id: snapcraft
+      with:
+        path: './test-projects/${{ matrix.project }}'
+        snapcraft-channel: 4.x/stable
+    - uses: actions/upload-artifact@v2
+      with:
+        name: 'snap'
+        path: ${{ steps.snapcraft.outputs.snap}}
+
   check-runner: # make sure the action works on each VM image
     strategy:
       matrix: