Use bundle_data and create_bundle to add support for iOS app bundle.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index 08c52c3ab9c20c78afe7642587cc6924fb30e762..5988ba5dd27fd3a3f1cfb47e451f10f600bd2c08 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -541,10 +541,9 @@ if (is_android) {
 # TODO(GYP) support use_system_icu.
 if (icu_use_data_file) {
   if (is_ios) {
-    group("icudata") {
-      # TODO(GYP): Provide an empty group so that this target does not
-      # unconditionally fail. The dat file needs to be bundled separately. In
-      # the longer term, need to figure out how to use system ICU
+    bundle_data("icudata") {
+      sources = [ "source/data/in/icudtl.dat" ]
+      outputs = [ "{{bundle_resources_dir}}/{{source_file_part}}" ]
     }
   } else {
     copy("icudata") {