Convert RLZ to a buildflag header

chrome/browser/BUILD.gn

Index: chrome/browser/BUILD.gn
diff --git a/chrome/browser/BUILD.gn b/chrome/browser/BUILD.gn
index f59ef266dbf77f162b662d1f1fc5646236fd284b..fb92e8a0c36147d28340991edbd2a77675820008 100644
--- a/chrome/browser/BUILD.gn
+++ b/chrome/browser/BUILD.gn
@@ -15,6 +15,7 @@ import("//media/media_options.gni")
 import("//net/features.gni")
 import("//ppapi/features/features.gni")
 import("//printing/features/features.gni")
+import("//rlz/features/features.gni")
 import("//sandbox/features.gni")
 import("//third_party/protobuf/proto_library.gni")
 import("//ui/base/ui_features.gni")
@@ -1510,6 +1511,7 @@ split_static_library("browser") {
     "//net:net_with_v8",
     "//ppapi/features",
     "//printing/features",
+    "//rlz/features",
     "//services/image_decoder/public/cpp",
     "//services/service_manager/public/cpp",
     "//skia",