[Chromecast] Replace 'fontconfig' GN target with dynamic dependency.

build/linux/BUILD.gn

Index: build/linux/BUILD.gn
diff --git a/build/linux/BUILD.gn b/build/linux/BUILD.gn
index 12994bca17075793000ef5c7ae1cc24da029a2bb..754859a56107899c74c26dc47dc495a89b4dde1b 100644
--- a/build/linux/BUILD.gn
+++ b/build/linux/BUILD.gn
@@ -11,6 +11,8 @@ gypi_values = exec_script("//build/gypi_to_gn.py",
                           "scope",
                           [ "system.gyp" ])
 
+use_system_fontconfig = !is_chromecast
+
 # If brlapi isn't needed, don't require it to be installed.
 if (use_brlapi) {
   config("brlapi_config") {
@@ -103,3 +105,13 @@ group("udev") {
     ":udev1_loader",
   ]
 }
+
+group("fontconfig") {
+  if (use_system_fontconfig) {
+    public_configs = [ "//build/config/linux:fontconfig" ]
+  } else {
+    public_deps = [
+      "//third_party/fontconfig",
+    ]
+  }
+}