Allow duplicate symbols on libcast_shell_android

This allows protobuf_full to be used.
The intention is to remove this after migrating away from protobuf_lite.

Bug: internal/167603683
Change-Id: Ida1171fb4d27b4a03f1de6dcf654e09e535f8cfe
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2401332Reviewed-by: Simeon Anfinrud <sanfin@chromium.org>
Commit-Queue: Ryan Chung <ryanchung@chromium.org>
Auto-Submit: Ryan Chung <ryanchung@chromium.org>
Cr-Commit-Position: refs/heads/master@{#846420}

chromecast/android/BUILD.gn

@@ -9,6 +9,10 @@ import("//media/media_options.gni")
 assert(is_android)
 
 cast_shared_library("libcast_shell_android") {
+  # TODO: Remove the ldflags after migrating away from protobuf_lite to
+  # protobuf_full.
+  ldflags = [ "-Wl,-z,muldefs" ]
+
   sources = [ "//chromecast/app/android/cast_jni_loader.cc" ]
 
   deps = [