CI: Add system dependencies

.github/workflows/crystal.yml

@@ -7,6 +7,23 @@ on:
     branches: [ master ]
 
 jobs:
+  test:
+    runs-on: ubuntu-latest
+
+    container:
+      image: crystallang/crystal
+
+    steps:
+    - uses: actions/checkout@v2
+    - name: Install system dependencies
+      run: |
+        apt-get update
+        apt-get install cmake 
+    - name: Install project dependencies
+      run: shards install
+    - name: Run tests
+      run: crystal spec
+
   build:
     runs-on: ubuntu-latest
 
@@ -15,7 +32,12 @@ jobs:
 
     steps:
     - uses: actions/checkout@v2
-    - name: Install dependencies
+    - name: Install system dependencies
+      run: |
+        apt-get update
+        apt-get install cmake 
+
+    - name: Install project dependencies
       run: shards install
     - name: Run tests
       run: crystal build