message: libevent: fix duplicate symbols on macOS
  Risk Level: low, macOS only
  Testing: n/a
  Docs Changes: n/a
  Release Notes: n/a
  Fixes: lyft/envoy-mobile#677
diff: @@ -129,6 +129,14 @@ envoy_cmake_external(
  },
  lib_source = "@com_github_libevent_libevent//:all",
  static_libraries = select({
  + # macOS organization of libevent is different from Windows/Linux.
  + # Including libevent_core is a requirement on those platforms, but
  + # results in duplicate symbols when built on macOS.
  + # See https://github.com/lyft/envoy-mobile/issues/677 for details.
  + "//bazel:apple": [
  + "libevent.a",
  + "libevent_pthreads.a",
  + ],
  "//bazel:windows_x86_64": [
  "event.lib",
  "event_core.lib",
  