Cover runtime core tests on CI (#311)

Summary: Pull Request resolved: #311

Differential Revision: D49215928

fbshipit-source-id: 1bcc8dad79c29cc04accd02c8ceeedb6f2a4ab84

Author: guangy10

.github/workflows/_unittest.yml

@@ -38,3 +38,5 @@ jobs:
         pip install .
         # Run pytest with coverage
         pytest --cov=./ --cov-report=xml
+        # Run gtest
+        buck2 test runtime/core/... runtime/platform/...