Add a no-rtti build to make our support official

Closes #11742

PiperOrigin-RevId: 506817491

.github/workflows/test_cpp.yml

@@ -20,6 +20,7 @@ jobs:
           - { name: MSAN, flags: --config=kokoro-msan }
           - { name: TSAN, flags: --config=tsan }
           - { name: UBSAN, flags: --config=ubsan }
+          - { name: No-RTTI, flags: --cxxopt=-fno-rtti }
         include:
           # Set defaults
           - image: us-docker.pkg.dev/protobuf-build/containers/test/linux/sanitize@sha256:dbd2f15fb69734d72c3fd10cb819bbe2ce4890acf49e9a2f9403983fe48e8807

src/google/protobuf/compiler/cpp/unittest.inc

@@ -1331,7 +1331,7 @@ TEST_F(GENERATED_SERVICE_TEST_NAME, CallMethod) {
 TEST_F(GENERATED_SERVICE_TEST_NAME, CallMethodTypeFailure) {
   // Verify death if we call Foo() with Bar's message types.
 
-#if GTEST_HAS_DEATH_TEST  // death tests do not work on Windows yet
+#if PROTOBUF_RTTI && GTEST_HAS_DEATH_TEST  // death tests do not work on Windows yet
   EXPECT_DEBUG_DEATH(
     mock_service_.CallMethod(foo_, &mock_controller_,
                              &foo_request_, &bar_response_, done_.get()),