add Coveralls token for macOS builds too

Author: Vladimir Kotal

.github/workflows/build.yml

@@ -55,6 +55,7 @@ jobs:
         OPENGROK_PULL_REQUEST: ${{ github.head_ref }}
         OPENGROK_REPO_SLUG: ${{ github.repository }}
         OPENGROK_REF: ${{ github.ref }}
+        OPENGROK_COVERALLS_TOKEN: ${{ secrets.COVERALLS_TOKEN }}
       run: ./dev/main
   windows:
     name: Windows with Java 11