ci: add a build for MSVC 2019 (#290)
ci: add a build for MSVC 2019 (#290)

Just a single static build for now, enough to verify we are not breaking
vcpkg and that the framework compiles. It uses
`FUNCTIONS_FRAMEWORK_CPP_TEST_EXAMPLES=OFF` to reduce the build times,
mostly that avoids `gRPC`, `protobuf`, and `google-cloud-cpp`.
GoogleCloudPlatform/functions-framework-cpp,GoogleCloudPlatform/functions-framework-cpp,GoogleCloudPlatform/functions-framework-cpp,GoogleCloudPlatform/functions-framework-cpp