[iOS] //rlz:rlz_id should not be build on iOS.

There is no point building this on iOS (if it needs to be build, it
probably should be build on the "host" not the "target").

BUG=459705

Review URL: https://codereview.chromium.org/1801043002

Cr-Commit-Position: refs/heads/master@{#381928}

rlz/BUILD.gn

@@ -120,14 +120,16 @@ test("rlz_unittests") {
   ]
 }
 
-executable("rlz_id") {
-  sources = [
-    "examples/rlz_id.cc",
-  ]
-  deps = [
-    ":rlz_lib",
-    "//build/config/sanitizers:deps",
-  ]
+if (!is_ios) {
+  executable("rlz_id") {
+    sources = [
+      "examples/rlz_id.cc",
+    ]
+    deps = [
+      ":rlz_lib",
+      "//build/config/sanitizers:deps",
+    ]
+  }
 }
 
 if (is_win) {