Fix gn_all, net_unittests build on GN ios.

BUILD.gn

Index: BUILD.gn
diff --git a/BUILD.gn b/BUILD.gn
index b8d4567b89eb30a61d93cff4cb5dc7ed18177a1e..6d4d92a08c021a686bdfb8c19118920520d59e04 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -741,10 +741,14 @@ group("gn_visibility") {
     # "//third_party/pdfium:pdfium_unittests",  # TODO(GYP): visibility?
 
     "//ui/resources:repack_ui_test_mac_locale_pack",
-
-    "//v8:v8_snapshot",
-    "//v8:postmortem-metadata",
   ]
+
+  if (!is_ios) {
+    deps += [
+      "//v8:v8_snapshot",
+      "//v8:postmortem-metadata",
+    ]
+  }
 }
 
 if (!is_ios) {