[Chromecast] Don't export symbols from libffmpeg.a

build/config/chromecast/BUILD.gn

Index: build/config/chromecast/BUILD.gn
diff --git a/build/config/chromecast/BUILD.gn b/build/config/chromecast/BUILD.gn
index a99ca5fb181056c6656195ff8777bf348a7b48b8..31edbea9147028ee5e9d7f9098ef68b1d90bba59 100644
--- a/build/config/chromecast/BUILD.gn
+++ b/build/config/chromecast/BUILD.gn
@@ -11,6 +11,10 @@ config("static_config") {
     # We want to statically link libstdc++/libgcc.
     "-static-libstdc++",
     "-static-libgcc",
+    # Don't allow visible symbols from libraries that contain
+    # assembly code with symbols that aren't hidden properly.
+    # http://b/26390825
+    '-Wl,--exclude-libs=libffmpeg.a',
   ]
 }