move to github actions

.github/workflows/coverage.yml

@@ -0,0 +1,16 @@
+name: coverage
+
+on: [push, pull_request]
+
+jobs:
+  build:
+    runs-on: macos-10.15
+    name: "coverage"
+    steps:
+    - uses: actions/checkout@v2
+      with:
+        submodules: recursive
+    - name: Install lcov by Homebrew
+      run: brew install lcov
+    - name: Build && Test && Upload
+      run: .ci/build_coverage.sh