ci: re-enable macOS tests (#8236)

.github/workflows/build.yml

@@ -23,14 +23,15 @@ jobs:
 
     strategy:
       matrix:
-        # disable macos-latest: https://github.com/actions/virtual-environments/issues/2247
-        os: [ubuntu-latest, windows-latest] # macos-latest
+        os: [ubuntu-latest, macos-latest, windows-latest]
         node-version: [12, 14]
         python-version: [3.8]
         java-version: [11]
         exclude:
           - os: windows-latest
             node-version: 12
+          - os: macos-latest
+            node-version: 12
 
     env:
       coverage: ${{ matrix.os == 'ubuntu-latest' && matrix.node-version == 14 }}