execute generator tests in CI

Author: vaind

.github/workflows/dart.yml

@@ -3,13 +3,24 @@ name: Dart CI
 on: [push, pull_request]
 
 jobs:
-  build:
+  generator:
+    runs-on: ubuntu-latest
+    container:
+      image:  google/dart:latest
+    steps:
+      - uses: actions/checkout@v1
+      - name: Change dir to the generator binary
+        run: cd bin/objectbox_model_generator
+      - name: Install dependencies
+        run: pub get
+      - name: Run tests
+        run: pub run test
 
+  lib:
+    needs: generator
     runs-on: ubuntu-latest
-    
     container:
       image:  google/dart:latest
-    
     steps:
     - uses: actions/checkout@v1
     - name: Install ObjectBox C-API