bazel: Add flatbuffers Swift hack
bazel: Add flatbuffers Swift hack

The generated code couldn't be used with private_deps because it
imported FlatBuffers normally and created a bunch of public types.
Ideally this would be an option to the generator instead of doing this.

This will have to be updated to a loop to support multiple input files

Signed-off-by: Keith Smiley <cadcacca0656fa2178c91a0e61e28374cd3a79c3@gmail.com>

envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile,envoyproxy/envoy-mobile