Add macOS and GCC tests.

.github/workflows/bazel_tests.yml

@@ -12,16 +12,21 @@ on:
 jobs:
 
   ubuntu:
-    runs-on: ubuntu-latest
+    runs-on: ${{ matrix.os }}
 
     strategy:
       matrix:
         include:
-          - { flags: "" }
-          - { flags: "--//:fasttable_enabled=true -- -cmake:test_generated_files" }
-          - { flags: "--config=asan -- -benchmarks:benchmark" }
+          - { CC: clang os: ubuntu-20.04 flags: "" }
+          # Some warnings only fire with -c opt
+          - { CC: clang os: ubuntu-20.04 flags: "-c opt" }
+          - { CC: gcc os: ubuntu-20.04 flags: "-c opt" }
+
+          - { CC: clang os: ubuntu-20.04 flags: "--//:fasttable_enabled=true -- -cmake:test_generated_files" }
+          - { CC: clang os: ubuntu-20.04 flags: "--config=asan -- -benchmarks:benchmark" }
+          - { CC: clang os: macos-11 flags: "" }
 
     steps:
       - uses: actions/checkout@v2
       - name: Run tests
-        run: cd ${{ github.workspace }} && bazel test ... ${{ matrix.flags }}
+        run: cd ${{ github.workspace }} && CC=${{ matrix.CC }} bazel test ... ${{ matrix.flags }}