Install dependencies for macOS

Author: hsbt

.github/workflows/test.yml

@@ -32,6 +32,11 @@ jobs:
       run: |
         sudo apt update -qy
         sudo apt install libgdbm6 libgdbm-dev
+    - name: Install packages
+      if: ${{ matrix.os == 'macos-latest' }}
+      run: |
+        brew update
+        brew install gdbm
     - name: Set up Ruby
       uses: ruby/setup-ruby@v1
       with: